Fluid Mechanics Pune University MCQs

 This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Introduction to Fluid Mechanics”.

1. Which one is in a state of failure?

a) Solid

b) Liquid

c) Gas

d) Fluid

Answer: d

Explanation: A fluid is a Tresca material with zero cohesion. In simple words, fluid is in a state of failure.

2. A small shear force is applied on an element and then removed. If the element regains it’s original position, what kind of an element can it be?

a) Solid

b) Liquid

c) Fluid

d) Gaseous

Answer: a

Explanation: Fluids  cannot resist even a small shear force and gets permanently deformed. Hence, the element must be a solid element.

3. In which type of matter, one won’t find a free surface?

a) Solid

b) Liquid

c) Gas

d) Fluid

Answer: c

Explanation: Solid molecules have a definite shape due to large inter-molecular forces. In liquids, molecules are free to move inside the whole mass but rarely escape from itself. Thus, liquids can form free surfaces under the effect of gravity. But, in case of gases, molecules tend to escape due to low forces of attraction. Thus, gases won’t form any free surface.

4. If a person studies about a fluid which is at rest, what will you call his domain of study?

a) Fluid Mechanics

b) Fluid Statics

c) Fluid Kinematics

d) Fluid Dynamics

Answer: b

Explanation: Fluid Mechanics deals with the study of fluid at rest or in motion with or without the consideration of forces, Fluid Statics is the study of fluid at rest, Fluid Kinematics is the study of fluid in motion without consideration of forces and Fluid Dynamics is the study of fluid in motion considering the application forces.

5. The value of the compressibility of an ideal fluid is

a) zero

b) unity

c) infinity

d) more than that of a real fluid

Answer: a

Explanation: Ideal fluids are incompressible which means they will have zero compressibility.

6. The value of the Bulk Modulus of an ideal fluid is

a) zero

b) unity

c) infinity

d) less than that of a real fluid

Answer: c

Explanation: Bulk modulus k is the reciprocal of compressibility fi.

k = 1 ⁄ fi

Ideal fluids are incompressible which means fi = 0. Thus, k will be infinity.

7. The value of the viscosity of an ideal fluid is

a) zero

b) unity

c) infinity

d) more than that of a real fluid

Answer: a

Explanation: Ideal fluids are non-viscous which means they will have zero viscosity.

8. The value of the surface tension of an ideal fluid is

a) zero

b) unity

c) infinity

d) more than that of a real fluid

Answer: a

Explanation: Ideal fluids haze zero surface tension but real fluids have some finite value of surface tension.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Fluid Properties – 1”.

1. Which one of the following is the unit of mass density?

a) kg = m 3

b) kg = m 2

c) kg = m

d) kg = ms

Answer: a

Explanation: Mass Density is defined as the mass per unit volume, i.e., p = m ⁄v

Thus, the unit of p is kg = m 3 .

2. The specific gravity of a liquid has

a) the same unit as that of mass density

b) the same unit as that of weight density

c) the same unit as that of specific volume

d) no unit

Answer: d

Explanation: The specific gravity of a liquid is the ratio of two similar quantities  which makes it unitless.

3. The specific volume of a liquid is the reciprocal of

a) weight density

b) mass density

c) specific weight

d) specific volume

Answer: b

Explanation: Specific volume is defined as the volume per unit mass.

v = v⁄m = 1 / m⁄v = 1⁄p

where p is the mass density.

4. Which one of the following is the unit of specific weight?

a) N = m 3

b) N = m 2

c) N = m

d) N = ms

Answer: a

Explanation: Specific weight is defined as the weight per unit volume, i.e.,

γ = w / v

Thus, unit of is N = m 3 .

5. Which one of the following is the dimension of mass density?

a) [M 1 L -3 T 0 ].

b) [M 1 L 3 T 0 ].

c) [M 0 L -3 T 0 ].

d) [M 0 L 3 T 0 ].

Answer: a

Explanation: Mass Density is defined as the mass per unit volume, i.e.,

[p] = [m]/[v] = [m] /[L 3 ] = [ML -3 ].

6. Which one of the following is the dimension of specific gravity of a liquid?

a) [M 1 L -3 T 0 ].

b) [M 1 L 0 T 0 ].

c) [M 0 L -3 T 0 ].

d) [M 0 L 0 T 0 ].

Answer: d

Explanation: The specific gravity of a liquid is the ratio of two similar quantities  which makes it dimensionless.

7. Which one of the following is the dimension of specific volume of a liquid?

a) [M 1 L -3 T 0 ].

b) [M -1 L 3 T 0 ].

c) [M -1 L -3 T 0 ].

d) [M 0 L 3 T 0 ].

Answer: b

Explanation: Specific volume is defined as the volume per unit mass. Thus,

[v] = [V]/[m] = [L 3 ]/[M] = [M -1 L 3 ].

8. Which one of the following is the dimension of specific weight of a liquid?

a) [ML -3 T -2 ].

b) [ML 3 T -2 ].

c) [ML -2 T -2 ].

d) [ML 2 T -2 ].

Answer: c

Explanation: Specific weight is defined as the weight per unit volume, i.e.,

fluid-mechanics-questions-answers-fluid-properties-q8

9. Two fluids 1 and 2 have mass densities of p1 and p2 respectively. If p1 > p2, which one of the following expressions will represent the relation between their specific volumes v1 and v2?

a) v1 > v2

b) v1 < v2

c) v1 = v2

d) Cannot be determined due to insufficient information.

Answer: b

Explanation: Specific volume is defined as the volume per unit mass.

v = v⁄m = 1 / m⁄v = 1⁄p

where p is the mass density. Thus, if p1 > p2, the relation between the specific volumes v1 and v2

will be represented by v1 < v2.

10. A beaker is filled with a liquid up to the mark of one litre and weighed. The weight of the liquid is found to be 6.5 N. The specific weight of the liquid will be

a) 6:5 kN = m 3

b) 6:6 kN = m 3

c) 6:7 kN = m 3

d) 6:8 kN = m 3

Answer: a

Explanation: Specific weight is defined as the weight per unit volume, i.e.,

γ = w⁄V

Thus, γ = 6:5 ⁄10 -3 N ⁄ m 3 = 6:5 kN/m 3 .

11. A beaker is filled with a liquid up to the mark of one litre and weighed. The weight of the liquid is found to be 6.5 N. The specific gravity of the liquid will be

a) 0.65

b) 0.66

c) 0.67

d) 0.68

Answer: b

Explanation: Specific gravity of a liquid is defined as the ratio of the density of the liquid to that of water.

fluid-mechanics-questions-answers-fluid-properties-q11

Thus, S = 0:66.

12. A beaker is filled with a liquid up to the mark of one litre and weighed. The weight of the liquid is found to be 6.5 N. The specific volume of the liquid will be

a) 1 l =kg

b) 1:5 l =kg

c) 2 l =kg

d) 2:5 l =kg

Answer: b

Explanation: Specific volume is defined as the volume per unit mass. Thus,

fluid-mechanics-questions-answers-fluid-properties-q12

This set of Fluid Mechanics Interview Questions and Answers focuses on “Fluid Properties – 2”.

1. Calculate the specific weight and weight of 20dm 3 of petrol of specific gravity 0.6.

a) 5886,117.2

b) 5886,234.2

c) 11772,117.2

d) None of the mentioned

Answer: a

Explanation: Specific weight = density*acceleration due to gravity

=.6*1000*9.81=5886N/m 3

Weight=volume*specific weight

=5886*0.02=117.2N.

2. If 200m 3 of fluid has a weight of 1060N measured on the planet having acceleration due to gravity 6.625m/s2, what will be it’s specific volume?

a) 0.8

b) 0.7

c) 0.9

d) 0.5

Answer: a

Explanation: Specific weight=Weight/volume

= /volume

=density*acceleration due to gravity

=1/

Specific volume=1060/.

3. For an incompressible fluid does density vary with temperature and pressure?

a) It varies for all temperature and pressure range

b) It remains constant

c) It varies only for lower values of temperature and pressure

d) It varies only for higher values of temperature and pressure

Answer: b

Explanation: For an incompressible fluid, the change in density is negligible. Thus it does not change with temperature and pressure.

4. Specific gravity is what kind of property?

a) Intensive

b) Extensive

c) None of the mentioned

d) It depends on external conditions

Answer: a

Explanation: It is independent of quantity of matter present.

5. If there is bucket full of oil and bucket full of water and you are asked to lift them, which one of the two will require more effort given that volume of buckets remains same?

a) Oil bucket

b) Water bucket

c) Equal effort will be required to lift both of them

d) None of the mentioned

Answer: b

Explanation: Density of water is more that oil. Hence, its weight for same volume of oil will also be higher. Therefore, more effort will be required.

6. If the fluid has specific weight of 10N/m 3 for a volume of 100dm 3 on a planet which is having acceleration due to gravity 20m/s2 , what will be its specific weight on a planet having acceleration due to gravity 4m/s2?

a) 5 N/m 3

b) 50 N/m 3

c) 2 N/m 3

d) 10 N/m 3

Answer: c

Explanation: For same volume, specific weight is directly proportional to acceleration due to gravity

Specific weight=4*10/20=2.

7. Should Specific Wieght of incompressible fluid only be taken at STP?

a) Yes, as specific weight may show large variation with temperature and pressure

b) No, it can be taken for any temperature and pressure

c) It should be taken at standard temperature but pressure may be any value

d) It should be taken at standard pressure but temperature may be any value

Answer: b

Explanation: Specific weight is inversely proportional to volume. For incompressible fluid , variation of volume with temperature and pressure is negligible for practical consideration. Therefore, specific weight remains constant.

8. An instrument with air as fluid was involved in some experiment which was conducted during day in desert. Due to some reason experiment couldn’t be conducted during day and had to be conducted during night. However there were considerable errors in obtained values. What might be the reason of these errors?

a) It was human error

b) It was instrumental error

c) Error was due to the fact that experiment was conducted at night

d) None of the mentioned

Answer: c

Explanation: In Desert areas, temperature at night is considerably lower than at day. Due to this air contracts at night. Hence, it’s specific volume changes. As specific volume was characteristic property utilized, results obtained showed error due to change in specific volume.

9. A stone weighed 177 N on earth. It was dropped in to oil of specific gravity 0.8 on a planet whose acceleration due to gravity is 5m/s2. It displaced oil having weight of 100N. What was the volume of oil displaced by the stone?

a) 25 Litres

b) 15 Litres

c) 25 m 3

d) None of the mentioned

Answer: a

Explanation: Volume displaced=oil displaced/=100/ .

10. An compressible fluid’s specific gravity was measured on earth, on a planet having acceleration due to gravity 5.5 times that of earth, and in space at STP. Where will it be having highest value?

a) on the earth

b) on the planet

c) in the space

d) it will be constant everywhere

Answer: d

Explanation: Specific gravity is characteristic property of fluid and is independent of external conditions.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Viscosity – 1”.

1. Water flows between two plates of which the upper one is stationary and the lower one is moving with a velocity V. What will be the velocity of the fluid in contact with the upper plate?

a) V

b) N ⁄ 2

c) 2V

d) 0

Answer: d

Explanation: According to the No-Slip condition, the relative velocity between the plate and the fluid in contact with it must be zero. Thus, the velocity of the fluid in contact with the upper plate is 0 and that with the lower plate is V.

2. The viscous force the relative motion between the adjacent layers of a fluid in motion.

Which one of the flowing fits best in the sentence?

a) opposes

b) never affects

c) facilitates

d) may effect under certain conditions

Answer: a

Explanation: Viscosity is the internal friction of a fluid in motion. It is the property by the virtue of which the relative motion between two adjacent fluid layers is opposed.

3. The viscosity of a fluid in motion is 1 Poise. What will be it’s viscosity  when the fluid is at rest?

a) 0

b) 0.5

c) 1

d) 2

Answer: c

Explanation: Viscosity is the property of a fluid and is constant for a given fluid under given conditions, irrespective of the fact whether the fluid is at rest or in motion.

4. Which of the following correctly states how the viscosities of a liquid and a gas will change with temperature?

a) Viscosity increases with the increase in temperature of a liquid and decreases with the increase in temperature of a gas

b) Viscosity increases with the increase in temperature of a liquid and increases with the increase in temperature of a gas

c) Viscosity decreases with the increase in temperature of a liquid and decreases with the increase in temperature of a gas

d) Viscosity decreases with the increase in temperature of a liquid and increases with the increase in temperature of a gas

Answer: a

Explanation: Viscosity of a liquid is due to the cohesion between it’s molecules. With the increase in temperature of a liquid, cohesion increases, leading to the rise in viscosity. Viscosity of a gas is due to the momentum transfer between it’s molecules. With the increase in the temperature of a liquid, molecular motion increases, leading to the fall in viscosity.

5. Which one of the following is not a unit of dynamic viscosity?

a) Pa-s

b) N-s/m 2

c) Poise

d) Stokes

Answer: d

Explanation: 

where F= viscous force, A= area, du ⁄ dx = velocity gradient, μ = co-effcient of viscosity. Therefore,

SI unit of μ is N-s/m 2 = Pa-s and CGS unit of μ is dyne-s/cm 2 . 1 Poise= 1 dyne-s/cm 2 and 1 Stokes= 1 cm 2 /s. Thus, Stokes is not an unit of μ, rather it is a unit of kinematic viscosity υ.

6. Which of the following is a unit of dynamic viscosity?

a) [M 1 L 1 T -1 ].

b) [M 1 L -1 T -1 ].

c) [M 1 L -2 T -2 ].

d) [M 1 L -2 T -2 ].

Answer: b

Explanation: 

where F= viscous force, A= area, du ⁄ dx = velocity gradient, μ = co-effcient of viscosity. Therefore,

fluid-mechanics-questions-answers-viscosity-q6

7. Which one of the following is the CGS unit of dynamic viscosity?

a) Stokes

b) Pa-s

c) m 2 /s

d) Poise

Answer: d

Explanation: 

where F= viscous force, A= area, du ⁄ dx = velocity gradient, μ = co-effcient of viscosity. Therefore,

CGS unit of μ is = dyne-s/cm 2 . 1 Poise= 1 dyne-s/cm 2 and 1 Stokes= 1 cm 2 /s. Thus, the CGS unit of μ will be Poise. Stokes is the CGS unit of kinematic viscosity.

8. The dynamic viscosity of a fluid is 1 Poise. What should one multiply to it to get the answer in N-s/m 2 ?

a) 0.1

b) 1

c) 10

d) 100

Answer: a

Explanation:

1 Poise = 1 dyne-s/cm 2 

9. Which of the following is a unit of kinematic viscosity?

a) Stokes

b) Pa-s

c) m2=s

d) Poise

Answer: a

Explanation: ν = μ/ρ, where ν = kinematic viscosity, μ = dynamic viscosity and ρ = density of the fluid. Unit of μ is dyne-s/cm 2 and that of ρ is kg/cm 3 .

Thus, the unit of ν is cm 2 /s = Stokes Poise is the unit of dynamic viscosity.

1 Poise = 1 dyne-s/cm 2 

10. Which of the following is the dimension of kinematic viscosity?

a) [L 1 T -1 ].

b) [L 1 T -2 ].

c) [L 2 T -1 ].

d) [L 2 T -2 ].

Answer: c

Explanation: ν = μ/ρ, where ν = kinematic viscosity, μ = dynamic viscosity and ρ = density of the fluid.

fluid-mechanics-questions-answers-viscosity-q10

11. The kinematic viscosity of a fluid is 0.1 Stokes. What will be the value is m 2 /s?

a) 10 -2

b) 10 -3

c) 10 -4

d) 10 -5

Answer: d

Explanation: 1Stokes = 1cm 2 /s = 10 -4 m 2 /s Therefore, 0.1Stokes = 10 -1 cm 2 /s = 10 -5 m 2 /s.

12. The shear stress at a point in a liquid is found to be 0.03 N/m 2 . The velocity gradient at the point is 0.15 s -1 . What will be it’s viscosity ?

a) 20

b) 2

c) 0.2

d) 0.5

Answer: b

Explanation: 

where F= viscous force, A= area, du ⁄ dx = velocity gradient, μ = co-effcient of viscosity. Therefore,

fluid-mechanics-questions-answers-viscosity-q12

13. The space between two plates , 1 cm apart, is filled with a liquid of viscosity 1 Poise. The upper plate is dragged to the right with a force of 5N keeping the lower plate stationary.

fluid-mechanics-questions-answers-viscosity-q13

What will be the velocity in m/s of flow at a point 0.5 cm below the lower surface of the upper plate if linear velocity profile is assumed for the flow?

a) 1.25

b) 2.5

c) 12.5

d) 0.25

Answer: c

Explanation: fluid-mechanics-questions-answers-viscosity-q13a

where F ν = viscous force, A = area, du ⁄ dx = velocity gradient, μ = co-effcient of viscosity. If linear velocity profile is assumed, du⁄dx = U/x, where U = velocity of the upper plate and x = distance between the two plates. Now, the viscous force Fv = -F= -5N. Substituting all the values in the equation, U becomes 12.5 m/s.

This set of Fluid Mechanics Questions and Answers for Freshers focuses on “Viscosity – 2”.

1. Two horizontal plates placed 250mm have an oil of viscosity 20 poises. Calculate the shear stress in oil if upper plate is moved with velocity of 1250mm/s.

a) 20 N/m 2

b) 2 N/m 2

c) 10 N/m 2

d) None of the mentioned

Answer:c

Explanation: Shear Stress = Viscosity * Velocity Gradient

= 20/10* 1.25/0.25

= 10 N/m 2 .

2. The kinematic viscosity of oil of specific gravity .8 is .0005 .This oil is used for lubrication of shaft of diameter .4 m and rotates at 190 rpm. Calculate the power lost in the bearing for a sleeve length of 90mm. The thickness of the oil film is 1.5mm.

a) 477.65 Watts

b) 955.31 Watts

c) 238.83 Watts

d) None of the mentioned

Answer: a

Explanation: Power lost= torque * angular velocity

= force* radius* angular velocity

= shear stress * area* radius* angular velocity

Shear Stress = viscosity* velocity gradient

Power lost= 0.0005*0.8*1000* 2*3.142*190/60*0.2*3.142*0.23 * 190/60

= 477.65 Watts.

3. Find the kinematic viscosity of oil having density 1962 g/m3. the force experienced for area of 20 m2 is 4.904 kN and velocity of gradient at that point is 0.2/s.

a) 0.625

b) 1.25

c) 2.5

d) None of the mentioned

Answer: a

Explanation: kinematic viscosity = dynamic viscosity / density

= /velocity gradient

= /

= .625.

4. The velocity distribution for fluid flow over a flat plate is given by u=2y-6y2 in which u is the velocity in metre per second at a distance of y metre above the plate. Determine the shear stress at y=0.15m.Take dynamic viscosity of fluid as 8.6 poise.

a) 0.172 N/m 2

b) 0.344 N/m 2

c) 0.086 N/m 2

d) None of the mentioned

Answer:a

Explanation: for y = 0.15m, velocity gradient = 0.2

viscosity= shear stress/velocity gradient

shear stress = 0.86*0.2 = 0.172N/m 2 .

5. In which types of fluids it is observed that momentum transfer dominates cohesive forces with increase in temperature and hence viscosity increases

a) Gases

b) Liquids

c) Solids

d) None of the mentioned

Answer:a

Explanation: It is the characteristic property of gases which show increase in viscosity with increase in temperature.

6. What is the characteristic variation shown by the thixotropic fluids in their shear stress vs. rate of shear strain graph?

a) shear stress increases with increase in rate of shear strain

b) shear stress decreases with increase in rate of shear strain

c) shear stress shows variation only after a definite shear stress is reached

d) shear stress has decreasing constant and then variation relationship with rate of shear strain

Answer: c

Explanation: Thixotropic fluid show a Non-Newtonian variation for shear stress vs. rate of shear strain graph after a characteristic limiting value of shear stress is reached.

7. What happens to viscosity in the case of incompressible fluids as temperature is increased?

a) It remains constant

b) It increases

c) It decreases

d) None of the mentioned

Answer: c

Explanation: In case of incompressible fluids, cohesive forces govern the viscosity. As temperature increases the cohesive forces between fluid molecules decreases due to increase in molecular agitation. Hence, as a result, viscosity decreases.

8. If a fluid, which has a constant specific gravity, is taken to a planet where acceleration due to gravity is 3 times compared to its value on earth, what will happen to its kinematic viscosity.

a) It increases

b) It decreases

c) It remains constant

d) None of the above

Answer: c

Explanation: Kinematic viscosity depends on density and dynamic viscosity. Both, density and dynamic viscosity, are independent of acceleration due to gravity. Therefore, kinematic viscosity is independent of acceleration due to gravity.

9. In liquids in order to measure the viscosity of fluid experimentally we consider the variation of shear stress with respect to what property?

a) strain

b) shear strain

c) rate of shear strain

d) none of the mentioned

Answer: c

Explanation: By definition, viscosity is shear stress per unit ‘rate of shear strain’.

10. For a compressible fluid the kinematic viscosity is affected by temperature and pressure variation.

a) True

b) False

Answer: a

Explanation: Viscosity shows variation for change in temperature and pressure for compressible fluids. Hence, kinematic viscosity is affected by temperature and pressure variation.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Vapor Pressure”.

1. Which of the following statement is true about vapor pressure of a liquid?

a) Vapor pressure is closely related to molecular activity and temperature of the liquid

b) Vapor pressure is closely related to molecular activity but independent of the temperature of the liquid

c) Vapor pressure is not affected by molecular activity and temperature of the liquid

d) Vapor pressure is not affected by molecular activity and is independent of the temperature of the liquid

Answer: a

Explanation: The vapor pressure of a liquid at a given temperature is given by the pressure ex-erted by the saturated vapor on the liquid surface. When the vapor is saturated, an equilibrium exists between the liquid and the vapor phases. The number of molecules leaving the liquid surface is equal to the number of molecules entering the liquid surface. Hence, it is obvious that vapor pressure will be related to molecular activity and consequently to temperature. With the increase in temperature molecular activity increases as a result of which vapor pressure increases.

2. Which of the following equation correctly depicts the relation between the vapor pressure of a liquid and it’s temperature?

a) Vapor pressure increases linearly with the increase in temperature of the liquid

b) Vapor pressure increases slightly with the increase in temperature of the liquid at low temperatures and the rate of increase goes high at higher temperatures

c) Vapor pressure increases rapidly with the increase in temperature of the liquid at low temperatures and the rate of increase goes low at higher temperatures

d) Vapor pressure remains unchanged with the increase in temperature of the liquid

Answer: b

Explanation: Vapor pressure is closely related to molecular activity which is in turn dependant on the temperature of the liquid. With the increase in temperature molecular activity of a vapor increases slowly at first and then rapidly. Similar is the nature of variaion of vapor pressure.

3. Which of the following is the condition for the boiling of a liquid?

a) Absolute pressure of a liquid must be greater than or equal to it’s vapor pressure

b) Absolute pressure of a liquid must be less than or equal to it’s vapor pressure

c) Absolute pressure of a liquid must be equal to it’s vapor pressure

d) Absolute pressure of a liquid must be greater than it’s vapor pressure

Answer: b

Explanation: As the absolute pressure of a liquid goes below it’s vapor pressure, the formation of vapor bubbles start. Thus, for boiling to start, the absolute pressure of a liquid must be less than or equal to it’s vapor pressure.

4. Which of the following machines have the possibility of cavitation?

a) Reaction turbines and centrifugal pumps

b) Reaction turbines and reciprocating pumps

c) Impulse turbines and centrifugal pumps

d) Impulse turbines and reciprocating pumps

Answer: a

Explanation: Cavitation occurs whenever absolute pressure of a liquid drops below it’s vapor pressure. Dropping of pressure is observed mainly in reaction turbines and centrifugal pumps.

5. The three liquids 1, 2, and 3 with vapor pressures V1, V2 and V3 respectively, are kept under same pressure. If V1 > V2 > V3, which liquid will start boiling early?

a) liquid 1

b) liquid 2

c) liquid 3

d) they will start boiling at the same time

Answer: a

Explanation: A liquid starts to boil whenever it’s absolute pressure drops below it’s vapor pressure. Thus, the absolute pressure of liquid 1 will drop early, as a result it’ll start boiling early.

6. Equal amount of a particular liquid is poured into three similar containers, namely 1, 2 and 3, at a temperature of T1, T2 and T3 respectively. If T1 < T2 < T3, the liquid in which container will have the highest vapor pressure?

a) container 1

b) container 2

c) container 3

d) the vapor pressure of the liquid will remain the same irrespective of it’s temperature

Answer: c

Explanation: Higher the temperature, higher is the molecular activity and consequently, higher is the vapor pressure of a given liquid. Since, container 3 is at the highest temperature, liquid in it will have the highest vapor pressure.

7. The absolute pressure of a water is 0.5kN above it’s vapor pressure. If it flows with a velocity of 1m/s, what will be the value of Cavitation Number describing the flow induced boiling?

a) 0.25

b) 0.5

c) 1

d) 2

Answer: c

Explanation: fluid-mechanics-questions-answers-vapor-pressure-q7

8. Which of the following is correct regarding the formation and collapse of vapor bubbles in a liquid?

a) Vapor bubbles are formed when the fluid pressure goes above the vapor pressure and collapses when the fluid pressure goes above the bubble pressure

b) Vapor bubbles are formed when the fluid pressure goes above the vapor pressure and collapses when the fluid pressure goes below the bubble pressure

c) Vapor bubbles are formed when the fluid pressure drops below the vapor pressure and collapses when the fluid pressure goes below the bubble pressure

d) Vapor bubbles are formed when the fluid pressure drops below the vapor pressure and collapses when the fluid pressure goes above the bubble pressure

Answer: d

Explanation: Whenever the absolute pressure of a fluid drops below it’s vapor pressure, bubble formation starts. Again, when the fluid pressure goes above the bubble pressure, it’ll collapse. This is how cavitation formation takes place.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Compressibility and Bulk Modulus”.

1. Which one of the following is the correct relation between compressibility β and Bulk Modulus k

a) β = k

b) β = 1/k

c) β = 2k

d) β = k/2

Answer: b

Explanation: Compressibility β of a liquid is deβned as the ratio of volumetric strain to the compressive stress while Bulk Modulus is the ratio of compressive stress to volumetric strain. Hence, β = 1/k is the correct relation.

2. Which one of the following is true about Bulk Modulus of elasticity?

a) it is the ratio of compressive stress to volumetric strain

b) it is the ratio of compressive stress to linear strain

c) it is the ratio of tensile stress to volumetric strain

d) it is the ratio of tensile stress to linear strain

Answer: a

Explanation: Bulk Modulus k is related to the compression of a liquid and the decrease in volume per unit volume. It is the ratio of compressive stress to the volumetric strain.

3. The value of the Bulk Modulus of elasticity for an incompressible fluid is

a) zero

b) unity

c) infinity

d) very low

Answer: c

Explanation: k = 1/β, where k= Bulk Modulus of elasticity and β= compressibility. For an incompressible fluid, β=0, thus the value of k will tend to infinity.

4. Three fluids 1, 2 and 3 have Bulk Moduli of k1, k2 and k3 respectively. If k1 > k2 > k3, which liquid will have the highest compressibility?

a) liquid 1

b) liquid 2

c) liquid 3

d) they’ll have equal compressibilities

Answer: c

Explanation: k = 1=β, where k= Bulk Modulus of elasticity and β= compressibility. If k1 > k2 > k3, then β1 < β2 < β3. Thus, liquid 3 will have the highest compressibility.

5. Bulk Modulus, Pressure, Force, Stress – Which one of these won’t have the same unit as the others?

a) Bulk Modulus

b) Pressure

c) Force

d) Stress

Answer: c

Explanation: The SI unit of Bulk Modulus, Pressure and Stress is N/m 2 but the unit of Force is N.

6. Which of the following is the dimension of Bulk Modulus?

a) [M 1 L -1 T -1 ].

b) [M 1 L -1 T -2 ].

c) [M 1 L 1 T -2 ].

d) [M 1 L 1 T -1 ].

Answer: b

Explanation:

7. Which one of the following is the unit of compressibility?

a) m=N

b) m 2 =N

c) m 3 =N

d) it is unitless

Answer: b

Explanation: k = 1/β, where k= Bulk Modulus of elasticity and β= compressibility.

Thus the unit of Bulk modulus is N/m 2 and the unit of compressibility becomes m 2 /N.

8. Which of the following is the dimension of compressibility?

a) [M 1 L 1 T -2 ].

b) [M 1 L 1 T -1 ].

c) [M -1 L 1 T -2 ].

d) [M -1 L 1 T 2 ].

Answer: d

Explanation: k = 1/β, where k = Bulk Modulus of elasticity and β= compressibility.

and [β] = [1/k] = [M -1 L 1 T 2 ].

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Types of Fluids”.

1. The relation between shear stress Z and velocity gradient  of a fluid is given by fluid-mechanics-questions-answers-types-fluid-q1d where A and n are constants. If n = 1, what type of fluid will it be?

a) Newtonian fluid

b) Non-Newtonian fluid

c) Pseudoplastic

d) Bingham plastic

Answer: a

Explanation: When n = 1, the relation reduces to Newton’s law of viscosity: z = A *  , where A will represent the viscosity of the fluid. The fluid following this relation will be a Newtonian fluid.

2. The relation between shear stress Z and velocity gradient  of a fluid is given by fluid-mechanics-questions-answers-types-fluid-q1d where A and n are constants. If n > 1, what type of fluid will it be?

a) Newtonian fluid

b) Dilatant

c) Pseudoplastic

d) Bingham plastic

Answer: b

Explanation: When n ≠ 1, the relation will be treated as Power law for Non-Newtonian fluids:

fluid-mechanics-questions-answers-types-fluid-q1d . For n > 1, the rate of change of the shear stress increases with the increase in the value of velocity gradient. Such fluids are called Dilatants.

3. The relation between shear stress Z and velocity gradient  of a fluid is given by fluid-mechanics-questions-answers-types-fluid-q1d where A and n are constants. If n < 1, what type of fluid will it be?

a) Newtonian fluid

b) Dilatant

c) Pseudoplastic

d) Bingham plastic

Answer: c

Explanation: When n ≠ 1, the relation will be treated as Power law for Non-Newtonian fluids:

fluid-mechanics-questions-answers-types-fluid-q1d . For n < 1, the rate of change of the shear stress decreases with the increase in the value of velocity gradient. Such fluids are called Pseudoplastics.

4. The relation between shear stress Z and velocity gradient  of a fluid is given by fluid-mechanics-questions-answers-types-fluid-q1d + B where A, n and B are constants. Which of the following conditions will hold for a Bingham plastic?

a) A = 0;B ≠ 0; n ≠ 1

b) A ≠ 0;B = 0; n ≠ 1

c) A = 0;B = 0; n = 1

d) A ≠ 0;B ≠ 0; n = 1

Answer: d

Explanation: For Bingham Plastics, shear stress will not remain constant after an yield value of stress. Thus, A ≠ 0;B ≠ 0. After the yield value, the relation between the shear stress and velocity gradient will become linear. hus, n = 1.

5. The relation between shear stress Z and velocity gradient  of a fluid is given by fluid-mechanics-questions-answers-types-fluid-q1d + B where A, n and B are constants. Which of the following conditions will hold for a Rheopectic?

a) A = 0;B ≠ 0; n > 1

b) A ≠ 0;B = 0; n < 1

c) A = 0;B = 0; n < 1

d) A ≠ 0;B ≠ 0; n > 1

Answer: d

Explanation: For Rheopectics, shear stress will not remain constant after an yield value of stress. Thus, A ≠ 0; B ≠ 0. After the yield value, the rate of change of the shear stress increases with the increase in the value of velocity gradient. Thus, n > 1.

6. The relation between shear stress Z and velocity gradient  of a fluid is given by fluid-mechanics-questions-answers-types-fluid-q1d + B where A, n and B are constants. Which of the following conditions will hold for a Thixotropic fluid?

a) A = 0;B ≠ 0; n > 1

b) A ≠ 0;B = 0; n > 1

c) A = 0;B = 0; n < 1

d) A ≠ 0;B ≠ 0; n < 1

Answer: d

Explanation: For Thixotropics, shear stress will not remain constant after an yield value of stress. Thus, A ≠ 0;B ≠ 0. After the yield value, the rate of change of the shear stress decreases with the increase in the value of velocity gradient. Thus, n < 1.

7. The graph shows relation between shear stress Z and velocity gradient  of a fluid is given by fluid-mechanics-questions-answers-types-fluid-q1d where A and n are constants. The graphs are drawn for three values of n. Which one will be the correct relationship between n 1 , n 2 and n 3 ?

fluid-mechanics-questions-answers-types-fluid-q7

a) n 1 > n 2 > n 3

b) n 1 < n 2 < n 3

c) n 1 > n 3 > n 2

d) n 1 < n 3 < n 2

Answer: b

Explanation: The graph corresponding to n = n1 represents Pseudoplastics, for which the rate of change of the shear stress decreases with the increase in the value of velocity gradient. The graph corresponding to n = n2 represents Newtonian fluids, for which shear stress changes linearly with the change in velocity gradient. The graph corresponding to n = n3 represents Dilatents, for which the rate of change of the shear stress increases with the increase in the value of velocity gradient.

8. Which of the following is a shear-thinnning fluid?

a) Bingham plastic

b) Rheopectic

c) Dilatant

d) Pseudoplastic

Answer: d

Explanation: Shear-thinning fluids are those which gets strained easily at high values of shear stresses. The relation between shear stress Z and velocity gradient  of a shear-thinning fluid is given by fluid-mechanics-questions-answers-types-fluid-q1d , where A and n are constants and n < 1. This relation is followed by Pseudoplastics.

9. Which of the following is a shear-thickening fluid?

a) Bingham plastic

b) Thixotropic

c) Dilatant

d) Pseudoplastic

Answer: c

Explanation: Shear-thickening fluids are those for which it gets harger to strain it at high values of shear stresses. The relation between shear stress Z and velocity gradient  of a shear-thickening fluid is given by fluid-mechanics-questions-answers-types-fluid-q1d where A and n are constants and n > 1. This relation is followed by Dilatants.

10. For what value of flow behaviour index, does the consistency index has a dimension independent of time?

a) 0

b) 1

c) 2

d) 3

Answer: c

Explanation: The relation between shear stress Z and velocity gradient  of a fluid is given by fluid-mechanics-questions-answers-types-fluid-q1d

where A is the flow consistency index and n is the flow behaviour index.

fluid-mechanics-questions-answers-types-fluid-q10

Thus [A] will be independent of time when n = 2.

11. What will be the dimension of the flow consistency index for a fluid with a flow behaviour index of 3?

a) [M L -2 T].

b) [M L -2 T -1 ].

c) [M L -1 T -2 ].

d) [M L -1 T].

Answer: d

Explanation: The relation between shear stress Z and velocity gradient  of a fluid is given by fluid-mechanics-questions-answers-types-fluid-q1d where A is the flow consistency index and n is the flow behaviour index. Putting n = 3,

fluid-mechanics-questions-answers-types-fluid-q11

12. What will be the dimension of the flow consistency index for a fluid with a flow behaviour index of -1?

a) N/m 2 s 2

b) N/m 2 s

c) N/ms

d) N/ms 2

Answer: b

Explanation: The relation between shear stress Z and velocity gradient  of a fluid is given by fluid-mechanics-questions-answers-types-fluid-q1d where A is the flow consistency index and n is the flow behaviour index. If n = -1, A = Z *  Unit of Z is N/m 2 and  is s -1 . Thus, the unit of A will be N/m 2 s.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Surface Tension”.

1. Which of the following contribute to the reason behind the origin of surface tension?

a) only cohesive forces

b) only adhesive forces

c) neither cohesive forces nor adhesive forces

d) both cohesive forces and adhesive forces

Answer: d

Explanation: The molecules on the surface of a liquid experience cohesive forces due to surrounding liquid molecules acting downward and adhesive forces due to surrounding gaseous molecules acting upwards. Surface tension orginates due to this unbalanced force on the surface molecules.

2. A soap film is trapped between a frame and a wire of length 10 cm as shown.

fluid-mechanics-questions-answers-surface-tension-q2

If the surface tension is given as 0.0049 N/m, what will be the value of m  such that the wire remains in equilibrium?

a) 0.1

b) 1

c) 10

d) 100

Answer: d

Explanation: For the wire to be in equilibrium, Force exerted by the film on the wire due to surface tension  must be equal to the downward force due to the weight of the wire . If σ=surface tension, l=length of the wire

2σl = mg

Substituting all the values, m = 2σl/g = 2 * 0.0049 * 0.01 ⁄ 9.81 = 99.9mg.

3. What will be the diameter  of a water droplet, the pressure inside which is 0.05 N/cm 2 greater than the outside pressure? 

a) 3

b) 0.3

c) 0.6

d) 6

Answer: c

Explanation: p = 4σ/d

where p = pressure difference between the liquid droplet and the surrounding medium, σ = surface tension and d = diameter of the droplet. Substituting all the values,

fluid-mechanics-questions-answers-surface-tension-q3

4. A soap bubble of d mm diameter is observed inside a bucket of water. If the pressure inside the bubble is 0.075 N/cm 2 , what will be the value of d? 

a) 0.4

b) 0.8

c) 1.6

d) 4

Answer: b

Explanation: p = 8σ/d

where p = pressure difference between the bubble and the surrounding medium, σ = surface tension and d = diameter of the bubble. Substituting all the values,

fluid-mechanics-questions-answers-surface-tension-q4

5. A liquid jet of 5 cm diameter has a pressure difference of N/m 2 . 

a) 12

b) 6

c) 3

d) 1.5

Answer: d

Explanation: p = σ/d

where p = pressure difference between the bubble and the surrounding medium, σ = surface tension and d = diameter of the bubble. Substituting all the values,

p = 0.075 / 5 * 10 -2 = 1.5 N/m 2 .

6. The rise in the level of a liquid in a tube is h. What will be the rise in the level if the same amount of liquid is poured into a tube of half the diameter.

a) 0

b) h/2

c) h

d) 2h

Answer: d

Explanation: fluid-mechanics-questions-answers-surface-tension-q5

where h = rise in liquid height in the tube, S = surface tension, θ = the angle of contact, d = diameter of the tube, ρ = density of liquid and g = acceleration due to gravity. All other factors remaining constant, h α d. Thus, if d is halved, h will be doubled.

7. The ratio of the surface tension S and density ρ of liquid 1 and 2 are 1:2 and 1:4 respectively. Equal amount of the two liquids is poured into two identical tubes. what will be the ratio of the rise in the liquid level in the two tubes? 

a) 1:2

b) 2:1

c) 8:1

d) 1:8

Answer: b

Explanation: fluid-mechanics-questions-answers-surface-tension-q5

where h = rise in liquid height in the tube, S = surface tension, θ = the angle of contact, d = diameter of the tube, ρ = density of liquid and g = acceleration due to gravity.

Given, S 1 / ρ 1 = 1 : 2 and S 2 / ρ 2 = 1 : 4.

fluid-mechanics-questions-answers-surface-tension-q7

8. The rise in the level of a liquid in a tube is h. If half the amount is poured outside, what will be the new rise in liquid level?

a) 0

b) h/2

c) h

d) 2h

Answer: c

Explanation: The rise in liquid level for a liquid is independent of the amount of liquid present in the tube. Since, same tube is used and same liquid is considered, the rise in the liquid level will remain the same.

9. If a glass tube of 10 mm diameter is immersed in water, what will be the rise or fall in capillary?

(Take surface tension = 0.075 N/m, g = 10 m/s 2 and angle of contact = 0)

a) 0.75

b) 1.5

c) 3

d) 6

Answer: c

Explanation: fluid-mechanics-questions-answers-surface-tension-q5

where h = rise in liquid height in the tube, S = surface tension, θ = the angle of contact, d = diameter of the tube, ρ = density of liquid and g = acceleration due to gravity. Substituting all the values,

10. A water drop of diameter 1 cm breaks into 1000 similar droplets of same diameter. What will be the gain or loss in the surface energy? 

a) gain of 0.424 mJ

b) gain of 0.212 mJ

c) loss of 0.212 mJ

d) loss of 0.424 mJ

Answer: b

Explanation: According to the Principle of Conservation of mass, M = 1000 * m, where M = mass of the big drop, m = mass of each droplet. Assuming density to be constant, D 3 = 1000 * d 3 , i.e. D = 10d, where D = diameter of big drop, d = diameter of a droplet.

Change in surface energy = Surface tension * Change in surface area = 0:075*(1000 * πd 2 – πD 2 ) = 0:075 * (10 * πD 2 – πD 2 ) = 0:075 * 9π *  2 = 0:212 mJ Since, the change is positive, there will be a gain in the surface energy.

This set of Fluid Mechanics Interview Questions and Answers for freshers focuses on “Thermodynamic Properties, Compressibility and Bulk Modulus”.

1. If there is no exchange of heat between system and surrounding where system comprises of a compressible fluid but the heat is generated due to friction, the process is an adiabatic.

a) True

b) False

Answer: b

Explanation: For process to be adiabatic, there is no heat exchange and no heat generation within fluid.

2. For a compressible fluid, if there is no change in specific volume at constant temperature, what type of process it is?

a) Isothermal process

b) Adiabatic Process

c) Polytropic process

d) None of the mentioned

Answer:a

Explanation: As, specific volume remains constant, density remains constant. Therefore for given temperature there is no change in volume. hence, the process is isothermal.

3. If the fluid is incompressible, do thermodynamic properties play an important role in its behaviour at varying temperature and pressure?

a) Yes

b) No

c) Depends on the fluid

d) None of the mentioned

Answer: b

Explanation: If fluid is incompressible there is not much change in observed properties with variation in temperature and pressure. Hence, no perceivable change.

4. If for same temperature and pressure change, the value of bulk modulus is compared for isothermal process and adiabatic process, which one would be higher?

a) Isothermal process

b) Adiabatic process

c) Value is constant for both the processes

d) None of the mentioned

Answer: b

Explanation: For isothermal process

K=p

For adiabatic process

K=kp

where K=Bulk modulus

k=Polytropic constant

p=Pressure.

5. The value of gas constant is same for all the gases

a) True

b) False

Answer: b

Explanation: The value of gas constant depends on molecular weight. As the molecular weight is different, gas constant will be different.

6. Calculate the pressure exerted by 9 kg of air at a temperature of 20℃ if the volume is 0.8m3. Assuming ideal gas laws are applicable.

a) 946 kN/m 2

b) 1892 kN/m 2

c) 1419 kN/m 2

d) None of the mentioned

Answer: a

Explanation: Ideal gas Law: PV=nRT

n=M/m

P=/28.97=946 kN/m 2 .

7. A gas weighs 16 N/m3 at 30℃ and at an absolute pressure of 0.35 N/mm 2 . Determine the gas constant.

a) 708.23

b) 354.11

c) 531.17

d) 1062.34

Answer:a

Explanation: R=P/=3500000*9.81/16*303=708.23.

8. A cylinder of 0.8 m3 in volume contains superheated steam at 70℃ and .4 N/m 2 absolute pressure. The superheated steam is compressed to .3 . Find pressure and temperature.

a) 0.74 N/m 2 , 422.3℃

b) 1.48 N/m 2 , 422.3℃

c) 0.74 N/m 2 , 844.6℃

d) 1.48 N/m 2 , 844.6℃

Answer: a

Explanation: For polytropic process,

P2=n *P1

=1.3 * 0.4 ……..

=.74 N/m2

T1=P1v1/nR=422.3℃.

9. Determine the compressibility of an incompressible fluid, if the pressure of the fluid is changed from 70 N/m 2 to 130 N/m 2 . The volume of the liquid changes by 0.15 percent.

a) 0.0025 m 2 /N

b) 0.0050 m 2 /N

c) 0.0070 m 2 /N

d) 0.0012 m 2 /N

Answer:a

Explanation: Compressibility=1/Bulk Modulus

=1/K

K=

=60/0.15

=400

Compressibility=.0025.

10. What is the variation of cp, cv and k in case of gases when the temperature increases?

a) cp and cv decreases with temperature, and k increases

b) cp and cv increase with temperature, and k decreases

c) cp and cv increase with temperature, and k increases

d) cp and cv decreases with temperature, and k decreases

Answer:b

Explanation: cp is molar heat capacity at constant pressure. As temperature is increased, enthalpy increases, heat capacity increases.

Same is for cv, cp is molar heat capacity at constant volume.

However cp-cv=R and cp/cv = R

Hence, as cp, cv increases R decreases.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Surface Tension, Capillarity, Vapour Pressure and Cavitation”.

1. Calculate the magnitude of capillary effect in millimeters in a glass tube of 7mm diameter, when immersed in mercury. The temperature of the liquid is 25℃ and the values of surface tension of mercury at 25℃ is 0.51 N/m. The angle of contact for mercury is 130°.

a) 140

b) 280

c) 170

d) 210

Answer: a

Explanation: Capillarity rise or fall

h=4*cosθ*σ/ρ*g*d

=4*cos130*0.51/13600*9.81*0.007

=140 mm.

2. Determine the minimum size of glass tube that can be used to measure water level if the capillary rise in the tube is restricted to 5mm. Consider surface tension of water in contact with air as 0.073 N/m

a) 5.95mm

b) 11.9mm

c) 2.97mm

d) 4.46mm

Answer: a

Explanation: d=4*cosθ*σ/ρ*g*h

=4*1*0.073/1000*9.81*0.005

=5.95mm.

3. An oil of vicosity 7 poise is used for lubrication between shaft and sleeve. The diameter of shaft is 0.6 m and it rotates is 360 rpm. Calculate the power lost in oil for a sleeve length of 160mm. The thickness of oil film is 1.0mm

a) 25.31 kW

b) 50.62 kW

c) 37.97 kW

d) 12.65 kW

Answer: a

Explanation: Power lost= torque * angular velocity

= force* radius* angular velocity

= shear stress * area* radius* angular velocity

Shear Stress = viscosity* velocity gradient

Power lost= 7916.8*3.142*0.3*0.3*0.3*2*3.142*60

= 25.31 kW.

4. Find the capillarity rise or fall if a capillary tube of diameter .03m is immersed in hypothetical fluid with specific gravity 6.5, surface tension 0.25 N/m and angle of contact 147°.

a) 0.44mm fall

b) 0.88mm fall

c) 0.44mm rise

d) 0.88mm rise

Answer: a

Explanation: h=4*cosθ*σ/ρ*g*d

=4*cos147*0.25/6.5*1000*9.81*0.03

=-0.44 mm i.e 0.44 mm fall.

5. Will capillary rise occur and if it occurs what will be capillary rise if glass capillarity tube is immersed in water and experiment is carried out by astronauts in space.

a) Capillarity rise will not occur

b) Capillarity rise will occur infinitely and will come out in form of fountain

c) Capillarity rise will occur finitely and will be the whole length of tube

d) None of the mentioned

Answer: c

Explanation: Capillary rise is given by

h=4*cosθ*σ/ρ*g*d

hence rise is inversely proportional to g

In space g is 0 m/s2

Hence, capillarity rise will occur finitely and will be the whole length of tube.

6. The surface tension of fluid in contact with air at 25℃ is 0.51N/m. The pressure inside a droplet is to be 0.05 N/cm2 greater than outside pressure. Determine the diameter of the droplet of water.

a) 4.08mm

b) 8.16mm

c) 2.04mm

d) None of the mentioned

Answer: a

Explanation: P=4*σ/d

d= 4*.51/500

=4.08 mm.

7. If a fluid of certain surface tension and diameter is used to create a soap bubble and a liquid jet. Which of the two, bubble or liquid jet, will have greater pressure difference on the inside and outside.

a) Liquid jet

b) Soap bubble

c) Both will have same pressure differrence

d) None of the mentioned

Answer: b

Explanation: For soap bubble,

P=8*σ/d

For liquid jet,

P=2*σ/d

Hence, soap bubble will be having more pressure difference.

8. Capillarity fall is reduced if we take the appartus  considerable distance inside the earth.

a) True

b) False

Answer: a

Explanation: Capillary rise is given by

h=4*cosθ*σ/ρ*g*d

Inside the earth, g  decreases. Hence, capillary rise will increase compared to that on the earth’s surface.

9. For liquid fluids will capillarity rise  increase or decrease with rise in temperature.

a) Increase

b) Decrease

c) Remain constant

d) First decrease then increase

Answer: b

Explanation: Capillary rise is given by

h=4*cosθ*σ/ρ*g*d

As temperature increases, σ decreases. Therefore, correspondingly rise will decrease as their is direct proportional relation between the two.

10. Cavitation is more pronounced in rough pipes than smooth surfaced pipes.

a) True

b) False

Answer: a

Explanation: Rough surfaced pipes have more friction with the fluid and hence possibility of cavitation is more pronounced.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Fluid Pressure”.

1. What is the pressure in Pascals at a depth of 1m below the water surface?

a) 98100 Pa

b) 980 Pa

c) 98 Pa

d) 1 Pa

Answer: a

Explanation: It’s the summation of weights on top of the water surface. In this case, it is the weight of the atmosphere and water above 1m. [Formula: P  = Patm +].

2. 15 bar equals to __________ Pascals.

a) 10 5 Pa

b) 1.5 x 10 6 Pa

c) 100 Pa

d) 1000 Pa

Answer: b

Explanation: Bar is a metric unit of pressure, but it does not fall under the SI units. One bar is exactly equal to a 100,000 Pascals. This value is taken from the atmospheric pressure on the earth at sea level.

3. The pressure at any given point of a non-moving fluid is called the ____________

a) Gauge Pressure

b) Atmospheric Pressure

c) Differential Pressure

d) Hydrostatic Pressure

Answer: d

Explanation: Hydrostatic pressure varies with the increase in depth. Hydrostatic pressure is measured from the surface of the fluid because of the increasing weight of the fluid. The fluid exerts a downward force from the surface of water thus making it a non-moving fluid.

4. The device used to measure the fluid pressure is _____________

a) Hygrometer

b) Calorimeter

c) Manometer

d) Thermometer

Answer: c

Explanation: Manometer is the most preferred measuring device as the pressure is measured by difference in the column heights of the manometer. It is expressed in terms of inches or centimeters of fluid making it easier for the conversion process.

5. What type of liquids are measured using a manometer?

a) Heavy liquids

b) Medium Liquids

c) Light Liquids

d) Heavy and light liquids

Answer: c

Explanation: Measurement of liquid in a manometer takes place through differential pressures by balancing the weight. Thus, it is easier for the manometer to measure liquids of lesser density than the heavier ones. Example of a light liquid is Water.

6. Which among these devices are the best suited for the measurement of high pressure liquids with high accuracy?

a) Dead Weight Gauge

b) Vacuum Gauge

c) Manganin wire pressure

d) Ionization Gauge

Answer: c

Explanation: Manganin wire is the most suitable measurement device for high pressure liquids. It has a high stability and durability on a long term basis. It also has a high hydrostatic pressure sensitivity and low strain sensitivity.

7. How do we measure the flow rate of liquid?

a) Coriolis method

b) Dead weight method

c) Conveyor method

d) Ionization method

Answer: a

Explanation: Coriolis concept of measurement of fluid takes place through the rotation with the reference frame. It is an application of the Newton’s Law. The device continuously records, regulates and feeds large volume of bulk materials.

8. What is the instrument used for the automatic control scheme during the fluid flow?

a) Rotameters

b) Pulley plates

c) Rotary Piston

d) Pilot Static Tube

Answer: d

Explanation: Pilot static tube is a system that uses an automatic control scheme to detect pressure. It has several holes connected to one side of the device. These outside holes are called as a pressure transducer, which controls the automatic scheme during fluid flow.

9. Define Viscosity?

a) Resistance to flow of an object

b) Resistance to flow of air

c) Resistance to flow of fluid

d) Resistance to flow of heat

Answer: c

Explanation: Viscosity is developed due to the relative motion between two surfaces of fluids at different velocities. It happens due to the shear stress developed on the surface of the fluid.

10. What is the viscosity of water at 30 o C?

a) 80.1

b) 0 .801

c) 801

d) 0.081

Answer: b

Explanation: A graph is plotted with temperature in the x-axis and dynamic viscosity in the y-axis. With the increase in pressure the viscosity decreases. It corresponds to an informal concept of thickness.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Pressure Distribution in a Fluid – 1”.

1. Which one of the following is the unit of pressure?

a) N

b) N/m

c) N/m 2

d) N/m 3

Answer: c

Explanation: Pressure is defined as the force per unit area acting normal to a surface. The SI unit of force is N and area is m 2 . Thus, the unit of pressure will be N = m 2 .

2. Which one of the following is the dimension of pressure?

a) [MLT 2 ].

b) [MLT -2 ].

c) [ML -1 T 2 ].

d) [ML -1 T -2 ].

Answer: d

Explanation: Pressure  is defined as the force  per unit area  acting normal to a surface.

Thus, 

3. Which one of the following statements is true regarding pressure?

a) Pressure is a scalar quantity

b) Pressure is a vector quantity

c) Pressure is a scalar quantity only when the area is infinitesimally small

d) Pressure is a vector quantity only when the area is infinitesimally small

Answer: a

Explanation: Pressure is defined as the force per unit area acting normal to a surface. Both force and area are vectors, but the division of one by the other leads to a scalar quantity.

4. A beaker half-filled with water is exposed to the atmosphere. If the pressure at points A, B and C as shown are P a , P b and P c respectively, which one of the following will be the relation connecting the three?

a) P a > P b = P c

b) P a > P b > P c

c) P a < P b < P c

d) P a < P b = P c

Answer: d

Explanation: Since the beaker is exposed to the atmosphere, the pressure at point A will be atmospheric, P a = 0. Pressure increases in the vertically downward direction, P a < P b and P a < P c .

Pressure remains constant in the horizontal direction, P b = P c . Therefore, P a < P b = P c .

5. A beaker is filled with a liquid up to a height h. If A and B are two points, one on the free surface and one at the base as shown, such that the minimum distance between the two is l, what will be the pressure at point B?

fluid-mechanics-questions-answers-pressure-distribution-constant-density-fluid-1-q5

Answer: b

Explanation: For a constant density liquid, pressure varies linearly in the vertically downward direction. Thus,

P B = P A + ρgh

where P B =Pressure at B, P A =Pressure at A, ρ=density of the liquid, g=acceleration due to gravity and h=vertical distance seP A rating the two points. Since A is at the free surface, P A = 0, P B = ρgh.

6. A beaker of height h is filled with a liquid of density ρ up to a certain limit. The beaker is rotated by an angle θ such that further increase in the angle will result in over flow of the liquid. If the liquid surface is exposed to the atmosphere, what will be the gauge pressure at point B?

a) ρgh

b) ρgh sin θ

c) ρgh cos θ

d) ρgh=2

Answer: c

Explanation: Vertical distance below the free surface at which the point B is located will be h cos θ.

Since the pressure at the free surface is atmospheric, the gauge pressure at B will be = 0 + ρgh cos θ.

7. An arm of a teapot is completely filled with tea  If the arm has a length of l and is inclined at 30 o to the horizontal, what will be the pressure difference between the two points, C at the mouth and D at the base of the arm?

a) ρgl

b) ρgl/2

c) √2ρgl

d) 2ρgl

Answer: b

Explanation: Vertical distance difference between the two points, C at the mouth and D at the base of the arm will be l sin θ = l sin 30 o = l=2. Thus, pressure difference between C and D is = ρgl/2.

8. A beaker is filled with a liquid of density ρ 1 up to a certain height. The pressure at the base of the beaker id P b . If the liquid is replaced by an equal volume of another liquid of density ρ 2 , what will be the pressure at the base of the beaker now?

Answer: d

Explanation: P B = ρ1gh, where h=height up to which the liquid is filled. Since equal volume of the second liquid is poured, it’ll also rise to a height of h. Thus, the pressure at the base will become

9. A beaker is filled with a liquid of density ρ1 up to a certain height. A is a point, h m downwards from the free surface of the liquid as shown. The liquid is replaced by equal volume of another liquid of density ρ2. If ρ1 > ρ2, how will the pressure at point A change?

fluid-mechanics-questions-answers-pressure-distribution-constant-density-fluid-1-q9

a) remain same

b) increase

c) decrease

d) become zero

Answer: c

Explanation: P 1 = ρ1gh and P 2 = ρ2gh, where P 1 and P 2 are the pressures at point A when liquids of density ρ1 and ρ2 are poured. If ρ 1 > ρ 2 , P 1 > P 2 . Thus the pressure at point A will decrease.

10. A beaker is filled with a liquid of density ρ1 up to a certain height. A is a point, h m downwards from the free surface such that the pressure at A is P. If the liquid is replaced by equal volume of another liquid of density ρ2, at what distance from the free surface will the pressure be P now?

fluid-mechanics-questions-answers-pressure-distribution-constant-density-fluid-1-q10

Answer: c

Explanation: P = ρ1gh. Let the point inside the liquid where the pressure is P be at a distance of h x from the surface. Thus, P = ρ2gh x . Hence, ρ1 * h = ρ2 * h x , ie, h x = ρ1/ρ2 h.

11. If the pressure at a point is 1m of water, what will be it’s value in terms of m of oil? 

a) 0.8

b) 1

c) 1.25

d) 2.5

Answer: c

Explanation: Pressure at a point P is equal to ρgh, where ρ is the density and h is the height of the liquid column. Therefore, ρ water * 1 * g = ρ oil * h * g, where h is the pressure in terms of m of oil.

Thus, h = ρ water / ρ oil = 1/0.8 = 1.25.

12. A beaker is filled with a liquid of density ρ up to a height h. If half the liquid is replaced by equal volume of another liquid of twice the density, what will be the change in the base pressure?

fluid-mechanics-questions-answers-pressure-distribution-constant-density-fluid-1-q12

a) increased by ρgh

b) decreased by ρgh

c) increased by ρgh=2

d) decreased by ρgh=2

Answer: c

Explanation: Base pressure when the beaker is filled with a liquid of density ρ up to a height h = ρgh

Base pressure when half the liquid is replaced by equal volume of another liquid of twice the density

= ρg h ⁄ 2 + 2ρg h ⁄ 2 = 3 ⁄ 2 ρgh

Thus the change in base pressure is = ρgh / 2. Since, P 2 > P 1 , there will be an increase in pressure.

13. A cuboidal container  is completely filled with water. A is a point, 25 cm above the base such that the pressure at point A is P. At what height  from the base will the pressure be 2P?

fluid-mechanics-questions-answers-pressure-distribution-constant-density-fluid-1-q13

a) 20

b) 15

c) 12.5

d) 10

Answer: a

Explanation: Pressure at a point P is equal to ρgh, where ρ is the density and h is the height of the liquid column from the top. Thus, ρ * g * = 2 * ρ * g *, where h from the base where the pressure will be 2P. Thus, h = 30 – 2 = 20.

14. A closed tank  is P A rtially filled with a liquid as shown. If the pressure of the air above the fluid is 2 bar, find the pressure at the bottom of the tank. Assume the density of the liquid to vary according to the following relation:

fluid-mechanics-questions-answers-pressure-distribution-constant-density-fluid-1-q14-1

where y is the height from the base

fluid-mechanics-questions-answers-pressure-distribution-constant-density-fluid-1-q14-2

a) 2.12

b) 2.15

c) 2.18

d) 2.5

Answer: c

Explanation: The change of pressure P with vertical direction y is given by

fluid-mechanics-questions-answers-pressure-distribution-constant-density-fluid-1-q14a

15. The pressure gauges 1, 2 and 3 are installed on the system as shown. If the readings of the gauges be P 1 = 1 bar, P 2 = 2bar and P 3 = 3 bar, what will be the value of P? (Take P atm = 1.01 bar)

fluid-mechanics-questions-answers-pressure-distribution-constant-density-fluid-1-q15

a) 3.01

b) 4.01

c) 6.01

d) 7.01

Answer: d

Explanation: P A = P Atm + P 1

P B = P A + P 2

P C = P B + P 3

P = P C = P Atm + P 1 + P 2 + P 3 = 1.01 + 1 + 2 + 3 = 7.01.

This set of Fluid Mechanics Questions and Answers for Experienced people focuses on “Pressure Distribution in a Fluid – 2”.

1. Three beakers 1, 2 and 3 of different shapes are kept on a horizontal table and filled with water up to a height h. If the pressure at the base of the beakers are P 1 , P 2 and P 3 respectively, which one of the following will be the relation connecting the three?

fluid-mechanics-questions-answers-experienced-q1

a) P 1 > P 2 > P 3

b) P 1 < P 2 < P 3

c) P 1 = P 2 = P 3

d) P 1 > P 2 < P 3

Answer: c

Explanation: The pressure on the surface of the liquid in the beakers is the same. Pressure varies in the downward direction according to the formula P = ρgh, where ρ is the density of the liquid and h is the height of the liquid column from the top.

P 1 = ρgh

P 2 = ρgh

P 3 = ρgh

Since all the beakers contain water up to to the same height, P 1 = P 2 = P 3 .

2. A beaker is filled with a liquid of specific gravity S = 1:2 as shown. What will be the pressure difference (in kN/m 2 ) between the two points A and B, 30 cm below and 10 cm to the right of point A?

fluid-mechanics-questions-answers-experienced-q2

a) 2.5

b) 3.5

c) 4.5

d) 5.5

Answer: b

Explanation: Pressure increases in the vertically downward direction but remains constant in the horizontal direction. Thus,

P B = P A + ρgh

where P B = Pressure at B, P A = Pressure at A, ρ = density of the liquid, g = acceleration due to gravity and h = vertical distance separating the two points.

PB – PA = 1:2 * 10 3 * 9.81 * 0.3 N/m 2 = 3.53 kN/m 2

3. The arm of a teapot is 10 cm long and inclined at an angle of 60 o to the vertical. The center of the arm base is 2 cm above the base of the beaker. Water is poured into the beaker such that half the arm is filled with it. What will be the pressure at the base of the beaker if the atmospheric pressure is 101.3 kPa?

fluid-mechanics-questions-answers-experienced-q3

a) 101.3

b) 101.5

c) 101.7

d) 101.9

Answer: c

Explanation: Total height of the water in the beaker = 2 + 1 ⁄ 2 * 10 cos 60 o cm = 4:5 cm. Pressure at the base of the beaker = 101.3 + 10 3 * 9.81 * 0.045 Pa = 101.3 + 0.44 kPa = 101.74 kPa.

4. A beaker of height 10 cm is half-filled with water (S w = 1) and half-filled with oil (S o = 1). At what distance  from the base will the pressure be half the pressure at the base of the beaker?

fluid-mechanics-questions-answers-experienced-q4

a) 4.375

b) 4.5

c) 5.5

d) 5.625

Answer: b

Explanation: Gauge pressure at the base of the beaker = S o * 10 3 * 0.05 * g + S w * 10 3 * 0.05 * g = 882.9Pa. Let the required height be h m from the base.

If 0.05 ≤ h < 0.1,

800g = 1 ⁄ 2 * 882.9

Thus, h = 0.04375 .

If 0 < h ≤ 0:05,

800 * 0.05 * g + 10 3 *  * g = 1 ⁄ 2 * 882.9

Thus, h = 0.045 . Hence, the correct answer will be 45 cm.

5. A beaker of height 30 cm is filled with water (S w = 1) up to a height of 10 cm. Now oil (S o = 0:9) is poured into the beaker till it is completely filled. At what distance  from the base will the pressure be one-third the pressure at the base of the beaker?

fluid-mechanics-questions-answers-experienced-q5

a) 27.33

b) 19.2

c) 10.8

d) 2.67

Answer: b

Explanation: Gauge pressure at the base of the beaker = S o * 10 3 * 0.2 * g + S w * 10 3 * 0.1 * g = 2550.6Pa. Let the required height be h m from the base.

If 0.1 ≤ h < 0.3,

800g = 1 ⁄ 3 * 2550.6

Thus, h = 0.192 .

Even if there’s no need to check for the other range, it’s shown here for demonstration purpose.If

0 < h ≤ 0.1,

800 * 0.2 * g + 10 3 *  * g = 1 ⁄ 3 * 2550.6

Thus, h = 0.2733 . Hence, the correct answer will be 19.2 cm.

6. An oil tank of height 6 m is half-filled with oil and the air above it exerts a pressure of 200 kPa on the upper surface. The density of oil varies according to the given relation:

fluid-mechanics-questions-answers-experienced-q6

What will be the percentage error in the calculation of the pressure at the base of the tank if the density is taken to be a constant equal to 800?

fluid-mechanics-questions-answers-experienced-q6a

a) 0.01

b) 0.05

c) 0.10

d) 0.15

Answer: a

Explanation: The change of pressure with the vertical direction y is given by

dP/dy = – ρg

dP = -ρg dy

If P a and P b be the pressures at the top and bottom surfaces of the tank,

fluid-mechanics-questions-answers-experienced-q6c

Thus, Pb = 223.5746kPa. If the density is assumed to be constant,

Pb = 200 + 800 * 9.81 * 3 * 10 3 = 223.544 kPa. Hence, precentage error fluid-mechanics-questions-answers-experienced-q6e

7. If a gas X be confined inside a bulb as shown, by what percent will the pressure of the gas be higher or lower than the atmospheric pressure? 

fluid-mechanics-questions-answers-experienced-q7

a) 4:75% higher

b) 4:75% lower

c) 6:75% higher

d) 6:75% lower

Answer: a

Explanation: P a = P atm = 101.3

P b = P a + 0.9 * 9.81 * 0.03 = 101.56

P c = P b + 13.6 * 9.81 * 0.04 = 106.9

P d = P c – 1 * 9.81 * 0.05 = 106.41

P e = P d – 0.9 * 9.81 * 0.04 = 106.1

P X = P e = 106.1

Since, P X > P atm , the percentage by which the pressure of the gas is higher than the atmospheric pressure will be fluid-mechanics-questions-answers-experienced-q7a

8. A tank of height 3 m is completely filled with water. Now two-third of the liquid is taken out and an equal amount of two other immiscible liquids of specific gravities 0.8 and 1.2 are poured into the tank. By what percent will the pressure at the base of the tank change?

fluid-mechanics-questions-answers-experienced-q8

a) 0%

b) 5%higher

c) 5%lower

d) 10%higher

Answer: a

Explanation: Pressure at the base initially = 1 * 9.81 * 3 = 29.43 kPa; Pressure at the base after adding the other two liquids= 0.8 * 9.81 * 1 + 1 * 9.81 * 1 + 1.2 * 9.81 * 1 kPa; Thus the pressure at the base remains the same.

9. A beaker of height 15 cm is completely filled with water. Now two-third of the liquid is taken out and an equal amount of two other immiscible liquids of specific gravities 0.8 and 1.2 are poured into the tank. What will be the pressure  at a point situated at a height, half the height of the beaker?

fluid-mechanics-questions-answers-experienced-q9

a) 588.6

b) 637.65

c) 735.75

d) 833.85

Answer: b

Explanation: PA = 0.8 * 10 3 * 9.81 * 0.05 + 1 * 10 3 * 9.81 * 0.025 = 637.65 kPa.

10. A beaker of height h is completely filled with water. Now two-third of the liquid is replaced by another liquid. If the pressure at the base of the beaker doubled, what is the specific gravity of the liquid poured?

a) 0.5

b) 1

c) 2

d) 2.5

Answer: d

Explanation: Pressure at the base initially = S w * h ⁄ 3 * g; Pressure at the base after pouring the second liquid = S w * h ⁄ 3 * g + S l * 2h ⁄ 3 * g, where S w and S l are the specific gravities of water and the second liquid.

fluid-mechanics-questions-answers-experienced-q10

11. A beaker, partially filled with a liquid is rotated by an angle 30 o as shown. If the pressure at point B becomes 12 bar, what will be the height  of the beaker?

fluid-mechanics-questions-answers-experienced-q11

a) 23.5

b) 24.5

c) 26.5

d) 27.5

Answer: b

Explanation: If the height of the beaker is h, the pressure at point B = 10 3 * g * h * cos 30 o = 12 * 10 3 kPa; h = 24.5 cm.

12. A beaker of height 15 cm is partially filled with a liquid and is rotated by an angle θ as shown.

If the pressure at point B becomes 5 bar, what will be the value of θ?

fluid-mechanics-questions-answers-experienced-q12

a) 30 o

b) 50 o

c) 60 o

d) 70 o

Answer: d

Explanation: If the angle of inclination is taken to be θ, the pressure at point B = 10 3 * g * 0.15 * cos θ = 5 * 10 3 kPa; θ = 70.12 o .

13. A beaker of height 30 cm is partially filled with a liquid and is rotated by an angle θ as shown.

At this point, the pressure at point B is found to be 5 bar. By what angle should θ be increased such that the pressure at B gets halved?

fluid-mechanics-questions-answers-experienced-q13

a) 12 o

b) 15 o

c) 17 o

d) 20 o

Answer: b

Explanation: Let θ 1 and θ 2 be the angles at which the beaker is inclided for the two cases mentioned.

10 3 * 9.81 * 0.15 * cos θ 1 = 5 * 100; θ 1 = 70.12 o

10 3 * 9.81 * 0.3 * cos θ 2 = 1 ⁄ 2 * 5 * 100; θ 1 = 85.12 o

θ 2 – θ 1 = 15 o

14. A closed tank  is partially filled with fluid as shown. If the pressure of the air above the fluid is 2 bar, find the pressure at the bottom of the tank. Assume the density ρ of the fluid to vary according to the given relation:

fluid-mechanics-questions-answers-experienced-q14

a) 766

b) 776

c) 786

d) 796

Answer: c

Explanation:

P A = P atm = 760

P B = P A + 30

P C = P B – 50 / 13.6 = 786.32

P X = P C = 786.3.

15. For what height of the mercury column will the pressure inside the gas be 40 cm Hg vacuum?

fluid-mechanics-questions-answers-experienced-q15

a) 36

b) 40

c) 76

d) 116

Answer: b

Explanation:

P gas = P atm – ρgH

Taking gauge pressure in terms of cm of Hg,

-40 = 0 – H; H = 40.

This set of Fluid Mechanics Interview Questions and Answers for Experienced people focuses on “Fluid Pressure at a Point & Pascal’s Law”.

1. A Hydraulic press has a ram of 30 cm diameter and a plunger of of 2 cm diameter. It is used for lifting a weight of 35 kN. Find the force required at the plunger.

a) 233.3 kN

b) 311.1 kN

c) 466.6 kN

d) 155.5 kN

Answer: d

Explanation: F/a=W/A

F=/

=155.5 kN.

2. The pressure at a point in the fluid is 4.9 N/cm2. Find height when the fluid under consideration is in oil of specific gravity of 0.85.

a) 5.83 m

b) 11.66 m

c) 17.49 m

d) 8.74 m

Answer: a

Explanation: Height=p/ρg

=48620/850*9.81

=5.83 m.

3. An open tank contains water upto a depth of 350 cm and above it an oil of specific gravity 0.65 for a depth of 2.5 m. Find the pressure intensity at the extreme bottom of the tank.

a) 5.027 N/cm 2

b) 10.05 N/cm 2

c) 2.51 N/cm 2

d) None of the mentioned

Answer: a

Explanation: p=  * 9.81

= 5.027 N/cm 2 .

4. The diameters of a small piston and a large piston of a hydraulic jack are 45 mm and 100 mm respectively.Force of 0.09 kN applied on smaller in size piston. Find load lifted by piston if smaller in size piston is 40 cm above the large piston. The density of fluid is 850 kg/m3

a) 60 N/cm 2

b) 12 N/cm 2

c) 30 N/cm 2

d) None of the mentioned

Answer: a

Explanation: Pressure at bottom of tank =ρgh + F/a

=850*9.81*0.4 + 90/3.142*0.045*0.045

=60 N/cm 2 .

5. If fluid is at rest in a container of a narrow mouth at a certain column height and same fluid is at rest at same column height in a container having broad mouth, will the pressure be different at certain depth from fluid surface.

a) Pressure will be same for both.

b) Pressure will be more for narrower mouth

c) Pressure will be less for narrower mouth

d) None of the mentioned

Answer: a

Explanation: As per hydrostatic law, the pressure depends only on the height of water column and not its shape.

6. We can draw Mohr’s circle for a fluid at rest.

a) True

b) false

Answer: b

Explanation: Mohr’s circle is used to denote shear stress distribution. For fluid at rest, there is no shear stress. Hence, we cannot draw Mohr’s circle for fluid at rest.

7. Pressure intensity or force due to pressure gradient for fluid at rest is considered as which kind of force?

a) Surface force

b) Body force

c) Force due to motion

d) None of the mentioned

Answer: a

Explanation: Pressure force is surface force.

8. Calculate the hydrostatic pressure for water moving with constant velocity at a depth of 5 m from the surface.

a) 49 kN/m2

b) 98 kN/m2

c) since fluid is in motion, we cannot analyse

d) None of the mentioned

Answer: a

Explanation: If fluid is moving with uniform velocity we treat it analytically same as if fluid is at rest

p= ρgh.

9. Pressure distribution for fluid at rest takes into consideration pressure due to viscous force.

a) True

b) False

Answer: b

Explanation: Viscous force term in pressure expression for fluid at rest is absent as their is no motion of liquid.

10. Barometer uses the principle of fluid at rest or pressure gradient for its pressure calculation.

a) True

b) False

Answer: a

Explanation: Principle of Barometer is Hydrostatic law.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Measurement of Pressure, Simple and Differential Manometers”.

1. The right limb of a simple U-tube manometer containing mercury is open to the atmosphere while the lift limb is connected to a pipe in which a fluid of specific gravity 0.85 is flowing. The centre of the pipe is 14 cm below the level of mercury in the right limb.Evaluate the pressure of fluid flowing in the pipe if the difference of mercury level in the two limbs is 22 cm.

a) 2.86 N/cm 2

b) 5.73 N/cm 2

c) 1.43 N/cm 2

d) None of the mentioned

Answer: a

Explanation: Pressure at centre of pipe + Pressure at depth 8 cm in left limb = Pressure at depth 22 cm in right limb

P = 13600×9.81×0.22 – 850×9.81×.08

= 2.86 N/cm 2 .

2. A single coloumn manometer is connected to a pipe containing a liquid of specific gravity 0.75. Find the pressure in the pipe if the area of reservoir is 250 times the area of tube for the manometer reading. The difference in mercury level is 40 cm. On the left limb the fluid is upto the height of 20 cm.

a) 10.42 N/cm 2

b) 5.21 N/cm 2

c) 2.60 N/cm 2

d) None of the mentioned

Answer: b

Explanation: Pressure = a/A height × + height in right limb × density of mercury × 9.81 – height in left limb × density of fluid × 9.81

= 5.21 N/cm 2

{ Here a/A = 1/ 250}.

3. A Differential manometer is connected at the points A and Bat the centre of two pipes. The pipe A contains a liquid of specific gravity = 1.5 while pipe B contains a liquid of specific gravity 0.85. The pressure at A and B are .5 kgf/cm 2 and 1.2 kgf/cm2 respectively. Find the difference in level of mercuru in the differential manometer. A is 2.5m above B and 5 m above the mercury in its own limb. B is 2.5 m above the mercury level in limb A.

a) 12.7 cm

b) 25.5 cm

c) 6.28 cm

d) 10.85 cm

Answer: a

Explanation: Total pressure at the datum line in limb A = Total pressure at the datum line in limb B\

0.5*9.81*10000 + 5*9.81*1500 + h*9.81*13600 = 1.2*9.81*10000 + *9.81*850

After solving,

h=12.7 cm.

4. An inverted differential manometer is connected to two pipes A and B which covey water. The fluid in manometer is oil of specific gravity 0.75. For the manometer readings, find the pressure difference between A and B. Datum in left limb is 40 cm above point A. Point B is 60 cm below datum line. Difference in level of fluid is 20 cm.

a) 1471 N/m 2

b) 2943 N/m 2

c) 735.75 N/m 2

d) None of the mentioned

Answer: a

Explanation: Total pressure at the datum line in limb A = Total pressure at the datum line in limb B

Pressure difference between A and B = -0.4*9.81*100 + 0.2*9.81*750 + 0.4*9.81*1000

= 1471 N/m 2 .

5. In the inverted U-tube Differential manometer, how is the specific gravity of manometric fluid used relative to the fluid flowing in the pipes

a) Specific gravity is more than that of fluid flowing in pipes

b) Specific gravity is less than that of fluid flowing in pipes

c) Specific gravity is equal to that of fluid flowing in pipes

d) None of the mentioned

Answer: b

Explanation: In the inverted U-tube Differential manometer, specific gravity of manometric fluid used is less than relative to the fluid flowing in the pipes as the manonmetric fluid is at the top.

6. Why is large reservoir used in single column manometer?

a) In order to enhance the change in level of liquid in reservoir

b) In order to negate the effects of change in level due to pressure variation

c) In order to reduce the effect due to dynamic pressure variation due to motion

d) None of the mentioned

Answer: b

Explanation: Single column manometer directly gives the pressure by measuring the height in the other limb and due to large cross sectional area of the reservoir, for any variation in pressure, the change can be neglected.

7. Manometers are the pressure measuring devices which use the principle of dynamic pressure to measure the pressure difference.

a) True

b) False

Answer: b

Explanation: Manometers are the pressure measuring devices which use the principle of pressure due to static fluid  to measure the pressure difference.

8. The distance moved by liquid will be more in which type of manometer?

a) Inclined Single coloumn manometer

b) Vertical Single coloumn manometer

c) Horizontal Single coloumn manometer

d) None of the mentioned

Answer: a

Explanation: The distance moved by liquid will be more in Inclined Single column manometer due to its inclination.

9. Differential manometer gives the pressure reading with respect to atmospheric pressure.

a) True

b) False

Answer: b

Explanation: Differential manometer gives the pressure difference between the fluid flowing in two pipes with respect to each other.

10. Which device is popularly used for measuring difference of low pressure?

a) Inverted U-tube Differential Manometer

b) U-tube Differential Manometer

c) Inclined Single column manometer

d) Vertical Single column manometer

Answer: a

Explanation: Inverted U-tube Differential Manometer has lighter manometric fluid, Hence it is used for measuring the low pressure difference.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Pressure at a Point in Compressible Fluid”.

1. If the atmospheric pressure at sea level is 7.5 N/cm2, determine the pressure at a height of 3000m assuming the pressure variation follows isothermal law. The density of air is given as 1.2 km/m3.

a) 4.68 N/cm 2

b) 9.37 N/cm 2

c) 2.34 N/cm 2

d) None of the mentioned

Answer: a

Explanation: pressure at any height Z = p*e -gZ/RT

=75000*e -9.81*3000*1.2/75000

= 4.68 N/cm 2 .

2. The barometric pressure at sea level is 760 mm of Mercury while that on a mountain top is 715 mm. If the density of air is assumed constant at 1.2 kg/m 3 , what is the elevation of the mountain top?

a) 510 m

b) 1020 m

c) 255 m

d) 128 m

Answer: a

Explanation: Gauge pressure at any height h = pressure at sea level – pressure at that height

h=-9.81*13600*0.715)/1.2*9.81

=510 m.

3. Calculate the pressure at a height of 6500m above the sea level if the atmospheric pressure is 10.145 N/cm2 and temperature is 25℃ assuming air is incompressible. Take density of air as 1.2 kg/m3. Neglect variation of g.

a) 4.98 N/cm 2

b) 2.49 N/cm 2

c) 1.24 N/cm 2

d) None of the mentioned

Answer: b

Explanation: Pressure= p – density of air*g*height

=101450-9.81*1.2*6500

= 2.49 N/cm 2 .

4. Calculate the pressure of air at a height of 3500m from sea level where pressure and temperature of air are 10 N/cm 2 and 25℃ respectively. The temperature lapse rate is given as 0.0065 ℃ /m. Take density of air at sea level equal to 1.2 kg/m 3 .

a) 19.7 N/cm 2

b) 9.85 N/cm 2

c) 4.93 N/cm 2

d) 6.24 N/cm 2

Answer: b

Explanation: pressure=p * *g*h*density/p) k/

=9.85 N/cm 2

Here, Lapse rate= -g/R*.

5. Pressure variation for compressible fluid is maximum for which kind of process?

a) Isothermal

b) Adiabatic

c) Quasi Static

d) None of the mentioned

Answer: a

Explanation: Due to constant temperature, pressure variation for compressible fluid is maximum for isothermal process.

6. Why can’t the density be assumed as constant for compressible fluids?

a) It shows variation with temperature and pressure

b) It remains constant with temperature and pressure

c) It becomes almost constant at very high temperature

d) None of the mentioned

Answer: a

Explanation: Volume and hence density changes with change in temperature and pressure.

7.What is the variation observed in temperature in atmosphere with respect to elevation?

a) It goes on decreasing with height

b) It goes on increasing with height

c) It first increases then decreases

d) It first decreases then increases

Answer: d

Explanation: It goes on decreasing first and shows increase after 32000 m.

8. As we go upwards, at height there is slight decrease in pressure variation.

a) True

b) False

Answer: a

Explanation: There is slight decrease in pressure as value of g  decreases slightly as we go higher.

9. For dynamic fluid motion in a pipe, the pressure measurement cannot be carried out accurately by manometer.

a) True

b) False

Answer: a

Explanation: For fluid moving with variable velocity, fluctuation in pressure is frequent and more in magnitude. Hence, we cannot use manometer.

10. A simple U tube manometer connected to a pipe in which liquid is flowing with uniform speed will give which kind of pressure?

a) Absolute Pressure

b) Vacuum Pressure

c) Gauge Pressure

d) None of the mentioned

Answer: c

Explanation: A simple U tube manometer will give pressure with respect to atmosphere. Hence, it is gauge pressure.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Hydrostatic Force on Plane Area – 1”.

1. A cuboidal beaker is half filled with water. By what percent will the hydrostatic force on one of the vertical sides of the beaker increase if it is completely filled?

a) 100

b) 200

c) 300

d) 400

Answer: c

Explanation: Hydrostatic force per unit width on a vertical side of a beaker = 1 ⁄ 2 * ρgh 2 , where ρ = density of the liquid and h= height of liquid column. The hydrostatic force when the beaker is completely filled = 1 ⁄ 2 ρg 2 = 2ρgh 2 .

Thus, percentage increase in hydrostatic force =  = 300%.

2. By what factor will the hydrostatic force on one of the vertical sides of a beaker decrease if the height of the liquid column is halved?

a) 1 ⁄ 2

b) 1 ⁄ 3

c) 1 ⁄ 4

d) 2 ⁄ 3

Answer: c

Explanation: Hydrostatic force per unit width on a vertical side of a beaker = 1 ⁄ 2 * ρgh 2 , where ρ = density of the liquid and h= height of liquid column. Thus, if the liquid column is halved, the hydrostatic force on the vertical face will become one-fourth.

3. Equal volume of two liquids of densities ρ1 and ρ2 are poured into two identical cuboidal beakers. The hydrostatic forces on the respective vertical face of the beakers are F 1 and F 2 respectively. If ρ1 > ρ2, which one will be the correct relation between F 1 and F 2 ?

a) F 1 > F 2

b) F 1 ≥ F 2

c) F 1 < F 2

d) F 1 ≤ F 2

Answer: a

Explanation: Hydrostatic force per unit width on a vertical side of a beaker = 1 ⁄ 2 * ρgh 2 , where ρ = density of the liquid and h= height of liquid column. Thus if ρ1 > ρ2, F 1 > F 2 and F 1 ≠ F 2 , when the h is constant.

4. Which of the following is the correct relation between centroid  and the centre of pressure  of a plane submerged in a liquid?

a) G is always below P

b) P is always below G

c) G is either at P or below it.

d) P is either at G or below it.

Answer: d

Explanation: The depth of the centroid y and the centre of pressure y CP are related by:

where I = the moment of inertia and A= area. None of the quantities I, A and y can be negative. Thus, Y CP > y . For horizontal planes, I = 0, hence Y CP = y

5. A beaker contains water up to a height of h. What will be the location of the centre of pressure?

a) h ⁄ 3 from the surface

b) h ⁄ 2 from the surface

c) 2h ⁄ 3 from the surface

d) h ⁄ 6 from the surface

Answer: c

Explanation: The depth of the centroid y and the centre of pressure y CP are related by:

where I = the moment of inertia and A = area. If y = h ⁄ 2 ; I = bh 3 /12 ;A = bh, then

fluid-mechanics-questions-answers-hydrostatic-force-plane-area-1-q5

6. A cubic tank is completely filled with water. What will be the ratio of the hydrostatic force exerted on the base and on any one of the vertical sides?

a) 1:1

b) 2:1

c) 1:2

d) 3:2

Answer: b

Explanation: Hydrostatic force per unit width on a vertical side of a beaker F v = 1 ⁄ 2 * ρgh 2 , where ρ = density of the liquid and h= height of the liquid column. Hydrostatic force per unit width on the base of the beaker = F b = ρgh * h = ρgh 2 . Thus, F b : F v = 2 : 1.

7. A rectangular lamina of width b and depth d is submerged vertically in water, such that the upper edge of the lamina is at a depth h from the free surface. What will be the expression for the depth of the centroid ?

a) h

b) h + d

c) h + d ⁄ 2

d) h + d / 2

Answer: c

Explanation: The centroid of the lamina will be located at it’s centre. ( d ⁄ 2 ). Thus, the depth of the centre of pressure will be h + d ⁄ 2 .

8. A rectangular lamina of width b and depth d is submerged vertically in water, such that the

upper edge of the lamina is at a depth h from the free surface. What will be the expression for the depth of the centre of pressure?

fluid-mechanics-questions-answers-hydrostatic-force-plane-area-1-q8

Answer: c

Explanation: The depth of the centroid y and the centre of pressure y CP are related by:

where I = the moment of inertia and A = area. If y = h + d ⁄ 2 ; I = bh 3 /12 ;A = bd. thus,

fluid-mechanics-questions-answers-hydrostatic-force-plane-area-1-q9

9. A square lamina  is submerged vertically in water such that the upper edge of the lamina is at a depth of 0.5 m from the free surface. What will be the total water pressure  on the lamina?

fluid-mechanics-questions-answers-hydrostatic-force-plane-area-1-q9a

a) 19.62

b) 39.24

c) 58.86

d) 78.48

Answer: c

Explanation: Total liquid pressure on the lamina = F = γ y A, where γ = specific weight of the liquid, y = depth of centroid of the lamina from the free surface, A= area of the centroid. Now, γ = 9:81 * 10 3 N / m 3 ; y = 0.5 + 1 ⁄ 2 * 2m = 1.5 m, A = 2 * 2 m 2 = 4 m 2 . Hence, F = 58.86 kN.

10. A square lamina  with a central hole of diameter 1m is submerged vertically in water such that the upper edge of the lamina is at a depth of 0.5 m from the free surface. What will be the total water pressure  on the lamina?

fluid-mechanics-questions-answers-hydrostatic-force-plane-area-1-q10

a) 15.77

b) 31.54

c) 47.31

d) 63.08

Answer: c

Explanation: Total liquid pressure on the lamina = F = γ y A, where γ = specific weight of the liquid, y = depth of centroid of the lamina from the free surface, A= area of the centroid. Now, γ = 9:81 * 10 3 N / m 3 ; y = 0.5 + 1 ⁄ 2 * 2m = 1.5 m, A = 2 * 2 – π ⁄ 4 * 1 2 m 2 = 3.215 m 2 Hence, F = 47.31 kN.

11. A square lamina  is submerged vertically in water such that the upper edge of the lamina is at a depth of 0.5 m from the free surface. What will be the depth  of the centre of pressure?

fluid-mechanics-questions-answers-hydrostatic-force-plane-area-1-q9a

a) 1.32

b) 1.42

c) 1.52

d) 1.72

Answer: d

Explanation: The depth of the centroid y and the centre of pressure y CP are related by:

where I = the moment of inertia and A = area. Now,

fluid-mechanics-questions-answers-hydrostatic-force-plane-area-1-q11a

fluid-mechanics-questions-answers-hydrostatic-force-plane-area-1-q11b

12. What will be the total pressure  on a vertical square lamina submerged in a tank of oil  as shown in the figure?

fluid-mechanics-questions-answers-hydrostatic-force-plane-area-1-q12

a) 26.5

b) 35.3

c) 44.1

d) 61.7

Answer: c

Explanation: Total liquid pressure on the lamina = F = γ y A, where γ = specific weight of the liquid, y = depth of centroid of the lamina from the free surface, A= area of the centroid. Now, γ = 9.81 * 0.9 * 10 3 N / m 3 ; y = 2.5m, A = 1 ⁄ 2 * 2 2 = 2 m 2 . Hence, F = 44.1 kN.

13. The upper and lower edges of a square lamina of length 4 m are at a depths of 1 m and 3 m respectively in water. What will be the depth  of the centre of pressure?

fluid-mechanics-questions-answers-hydrostatic-force-plane-area-1-q13

a) 1.33

b) 1.57

c) 2.17

d) 2.33

Answer: c

Explanation: The depth of the centroid y and the centre of pressure y CP are related by:

fluid-mechanics-questions-answers-hydrostatic-force-plane-area-1-q13a

where I= the moment of inertia and A = area and θ = the angle of inclination of the lamina to the horizontal. Now,

fluid-mechanics-questions-answers-hydrostatic-force-plane-area-1-q13b

= 2:17m.

14. The upper and lower edges of a square lamina of length 4 m are at a depths of 1 m and 3 m respectively in water. What will be the total pressure  on the lamina?

fluid-mechanics-questions-answers-hydrostatic-force-plane-area-1-q13

a) 156.96

b) 235.44

c) 313.92

d) 392.4

Answer: c

Total liquid pressure on the lamina = F = γ y A, where γ = specific weight of the liquid, y = depth of centroid of the lamina from the free surface, A= area of the centroid. Now, γ = 9:81 * 0.9 * 10 3 N / m 3 ; y = 1 + 3-1 / 2 = 2m, A = 4 * 4 = 16 m 2 . Hence, F = 313.92 kN.

Answer: c

Explanation: The depth of the centroid y and the centre of pressure y CP are related by:

where I = the moment of inertia and A = area. Each side of the lamina = 3/&sqrt;2 Now, y = 1 + 3 ⁄ 2 = 1.5,

Sanfoundry Global Education & Learning Series – Fluid Mechanics.

This set of Fluid Mechanics test focuses on “Hydrostatic Force on Plane Area – 2”.

1. The greatest and the least depth of a circular plate of 4 m diameter from the free surface of water are 3m and 1 m respectively as shown. What will be the total pressure in  on the plate?

fluid-mechanics-questions-answers-hydrostatic-force-plane-area-1-q13

a) 123

b) 185

c) 246

d) 308

Answer: c

Explanation: Total liquid pressure on the lamina = F = γ y A, where γ = specific weight of the liquid, y = depth of centroid of the lamina from the free surface, A= area of the centroid. Now, γ = 9.81 * 10 3 N / m 3 ; y = 1 + 3 – 1 / 2 – 2m, A = π ⁄ 4 * 4 2 = 4π m 2 . Hence, F = 246.55 kN.

2. The greatest and the least depth of a circular plate of 4 m diameter from the free surface of water are 3m and 1 m respectively as shown. What will be the depth  of it’s centre of pressure?

fluid-mechanics-questions-answers-hydrostatic-force-plane-area-1-q13

a) 1.125

b) 1.25

c) 2.125

d) 2.25

Answer: c

Explanation: The depth of the centroid y and the centre of pressure y CP are related by:

fluid-mechanics-questions-answers-hydrostatic-force-plane-area-1-q13a

where I= the moment of inertia and A = area and θ = the angle of inclination of the lamina to the horizontal. Now,

y = 1 + 3 – 1 / 2 = 2, I = π ⁄ 64 * 4 2 = 4π, A = π ⁄ 4 * 4 2 = 4π, sin θ = 1 ⁄ 2 Thus, y CP = 2.125m.

3. The highest and lowest vertices of a diagonal of a square lamina  are 1 m and 3 m respectively as shown. What will be the water force  on the lamina?

fluid-mechanics-questions-answers-hydrostatic-force-plane-area-1-q13

a) 78

b) 118

c) 157

d) 196

Answer: c

Explanation: Total liquid pressure on the lamina = F = γ y A, where γ = specific weight of the liquid, y = depth of centroid of the lamina from the free surface, A= area of the centroid. Now, γ = 9.81 * 10 3 N / m 3 ; y = 1 + 3 – 1 / 2 = 2m, each side of the lamina = fluid-mechanics-questions-answers-test-q3

Hence, F = 156:96 kN.

4. The highest and lowest vertices of a diagonal of a square lamina  are 1 m and 3 m respectively as shown. What will be the depth  of it’s centre of pressure?

fluid-mechanics-questions-answers-hydrostatic-force-plane-area-1-q13

a) 1.08

b) 1.58

c) 2.08

d) 2.58

Answer: c

Explanation: fluid-mechanics-questions-answers-hydrostatic-force-plane-area-1-q13a

where I = the moment of inertia and A= area and θ = the angle of inclination of the lamina to the horizontal. Now, y = 1 + 3 – 1 / 2 = 2m, each side of the lamina = =8; sin θ = 3-1/4 = 1 ⁄ 2 . Thus, y CP = 2.08m.

5. A square lamina  is submerged vertically in water such that the upper edge of the lamina is at a depth of 0.5 m from the water surface. If the pressure on the surface is 12 bar, what will be the total water pressure  on the lamina?

fluid-mechanics-questions-answers-test-q5

a) 39

b) 59

c) 64

d) 71

Answer: c

Explanation: Total liquid pressure on the lamina = F = γ y A, where γ = specific weight of the liquid, y = depth of centroid of the lamina from the free surface, A= area of the centroid. Now, γ = 9.81 * 10 3 N / m 3 ; fluid-mechanics-questions-answers-test-q5a A = 2 * 2 = 4 m 2 . Hence, F = 63.65 kN.

6. A container is lled with two liquids of densities ρ1 and ρ2 up to heights h 1 and h 2 respectively. What will be the hydrostatic force  per unit width of the lower face AB?

fluid-mechanics-questions-answers-test-q6a

Answer: c

Explanation: Total liquid pressure on the lamina = F = γ y A, where γ = specific weight of the liquid, y = depth of centroid of the lamina from the free surface, A= area of the centroid. Now,

fluid-mechanics-questions-answers-test-q6b

7. A container is lled with two liquids of densities ρ and 2ρ up to heights h and eh respectively. What will be the ratio of the total pressure on the lower face AB and on the upper face BC?

fluid-mechanics-questions-answers-test-q7

a) 1 : 1

b) 3 : 1

c) 2 : 1

d) 3 : 2

Answer: b

Explanation: Total liquid pressure on the lamina = F = γ y A, where γ = specific weight of the liquid, y = depth of centroid of the lamina from the free surface, A= area of the centroid.

fluid-mechanics-questions-answers-test-q7a

8. A container is lled with two liquids of densities ρ and 2ρ up to heights h and eh respectively. What will be the ratio of the depths of the centres of pressure of the upper face BC and the lower face AB?

fluid-mechanics-questions-answers-test-q7

a) 1 : 2

b) 3 : 4

c) 2 : 3

d) 3 : 2

Answer: c

Explanation: fluid-mechanics-questions-answers-test-q8

9. A gate of length 5 m is hinged at A as shown to support a water column of height 2.5 m. What should be the minimum mass per unit width of the gate to keep it closed?

fluid-mechanics-questions-answers-test-q9

a) 3608

b) 4811

c) 7217

d) 9622

Answer: d

Explanation: To keep the gate closed, moment due to weight of the gate should be balanced by the moment due to the hydrostatic force.

fluid-mechanics-questions-answers-test-q9a

where m = mass of the plate, θ = angle of inclination to the horizontal, F hyd = hydrostatic force on

the plate, x = distance of the point of action of F hyd from the hinge point = 2 ⁄ 3 * 5 = 10 ⁄ 3

fluid-mechanics-questions-answers-test-q9b

F hyd = γ y A, where γ = specific weight of the liquid = 9.81 * 10 3 y = depth of the centre of pressure from the free surface = 2.5/2 = 1.25 and A = 5 * 1. Substituting all the values in the equation, we get m = 9622.5g.

10. A large tank is lled with three liquids of densities ρ1, ρ2 and ρ3 up to heights of h 1 , h 2 and h 3 respectively. What will be the expression for the instantaneous velocity of discharge through a small opening at the base of the tank? 

fluid-mechanics-questions-answers-test-q10

Answer: d

Explanation: Instantaneous velocity of discharge  where h= height of the liquid column.

fluid-mechanics-questions-answers-test-q10a

11. A large tank of height h is filled with a liquid of density ρ. A similar tank is half-filled with this liquid and other-halffilled with another liquid of density 2ρ as shown. What will be the ratio of the instantaneous velocities of discharge through a small opening at the base of the tanks? 

fluid-mechanics-questions-answers-test-q11

a) 2 : 3

b) 2 : √3

c) √2 : 3

d) √2 : √3

Answer: d

Explanation: Instantaneous velocity of discharge  where h= height of the liquid column.

fluid-mechanics-questions-answers-test-q11a

12. A large tank of height h is half-filled with a liquid of density ρ and other half-filled with a liquid of density 4ρ. A similar tank is half-filled with a liquid of density 2ρ and other-half filled with another liquid of density 3ρ as shown. What will be the ratio of the instantaneous velocities of discharge through a small opening at the base of the tanks? 

fluid-mechanics-questions-answers-test-q12

a) 1 : 1

b) 1 : 2

c) 2 : 1

d) 1 : 3

Answer: a

Explanation: Instantaneous velocity of discharge  where h= height of the liquid column.

fluid-mechanics-questions-answers-test-q12b

fluid-mechanics-questions-answers-test-q12c

13. A large tank is filled with three liquids of densities ρ, 2ρ and 3ρ up to a height of h ⁄ 3 each. What will be the expression for the instantaneous velocity of discharge through a small opening at the base of the tank? 

fluid-mechanics-questions-answers-test-q13

Answer: c

Explanation: Instantaneous velocity of discharge  where h= height of the liquid column.

fluid-mechanics-questions-answers-test-q13a

14. A large tank is filled with three liquids of densities ρ, 2ρ and 3ρ up to heights of h ⁄ 6 , h ⁄ 3 and h ⁄ 2 respectively. What will be the ratio of the instantaneous velocity of discharge through a small opening at the base of the tank in this case to that if the container is filled with the liquid of density ρ only? 

fluid-mechanics-questions-answers-test-q14

Answer: d

Explanation: Instantaneous velocity of discharge  where h= height of the liquid column.

fluid-mechanics-questions-answers-test-q14a

This set of Fluid Mechanics Quiz focuses on “Total Pressure & Vertical Plane Surface Submerged in a Liquid”.

1. Does total pressure takes into the account force exerted by the fluid when it is in the dynamic motion?

a) Yes

b) No

c) Depends on the conditions

d) Depends on the type of Motion

Answer:b

Explanation: Total pressure is defined only for the static fluid at rest. There is no dynamic component as no motion is involved.

2. Can centre of pressure for a vertical plane submerged surface be ever be above centre of Gravity

a) Yes

b) No

c) It can be above in cases where the surface height is very large

d) None of the mentioned

Answer: b

Explanation: Centre of pressure always lies below the centre of gravity. In certain cases it may coincide but it can never be above the centre of gravity.

3. Which principle is used for calculating the centre of pressure?

a) Principle of momentum

b) Principle of conservation of energy

c) Principle of balancing of momentum

d) None of the mentioned

Answer: c

Explanation: We balance the moment in order to calculate the position of centre of pressure.

4. In a vertically submerged plane surface, pressure at evbery point remains same

a) True

b) False

Answer: b

Explanation: Pressure at every point is different as the depth of different point from is different.

5. The magnitude of total pressure and centre of pressure is independent on the shape of the submerged plane surface.

a) True

b) False

Answer: b

Explanation: For differently shaped surfaces, the area and hence position of centroid will be different. Hence, the magnitude of total pressure and centre of pressure is dependent on the shape of the submerged plane surface.

6. What is the variation of total pressure with depth for any submerged surface if we neglect variation in the density?

a) Linear

b) Parabolic

c) Curvilinear

d) Logarithmic

Answer: a

Explanation: Total pressure is given by,

F=w*a*y

hence, F ∝ y i.e linear relation.

7. A pipe line which is 6 m in diameter contains a gate valve. The pressure at the centre of the pipe is 25 N/cm2. If the pipe is filled with specific gravity 0.8, find the force exerted by the oil upon the gate.

a) 7.06 MN

b) 14.12 MN

c) 3.53 MN

d) 28.24 MN

Answer: a

Explanation: ĥ=p/ρg

=250000/9.81*800

=31.855 m

F=wAĥ

=9.81*800*9*π*31.855

=7.06 MN.

8. Determine the centre of pressure on an isosceles triangle plate of base 6m and altitude 6m when it is immersed vertically in an oil of specific gravity 0.75. The base of the plate coincides with the free surface of oil.

a) 6 m

b) 3 m

c) 9 m

d) 12 m

Answer: b

Explanation: ŷ=I/Aĥ + ĥ

I=bh³/36

ŷ=36*2/18 + 2

=3 m.

9. A tank contains water upto a height of 0.5 m above the base. An immiscible liquid of specific gravity 0.75 is filled on the top of water upto 1.5 m height. Calculate total pressure on side of the tank.

a) 17780.61 N/m2

b) 35561.22 N/m2

c) 71122.44 N/m2

d) 8890.31 N/m2

Answer: a

Explanation: F = F1 + F2 + F3

F=w*A*ŷ

F= 8277.18+5518.12+3985.31

= 17780.61 N/m 2 .

10. A circular opening, 6m diameter, in a vertical side of a tank is closed by a disc of 6m diameter which can rotate about a horizontal diameter. Calculate the force on the disc. The centre of circular opening is at the depth of 5 m.

a) 1.38 MN

b) 2.76 MN

c) 5.54 MN

d) 7.85 MN

Answer: a

Explanation: F=w*A*ŷ

=9.81*1000*3.142*3 2 *5

=1.38 MN.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Horizontal and Inclined Plane Surface Submerged in a Liquid”.

1. Find the total pressure on a rectangular plate of dimensions 2×3 m immersed in a fluid of specific gravity 0.65 at a depth of 6 m from the surface.

a) 22.9 N/cm 2

b) 45.8 N/cm 2

c) 11.5 N/cm 2

d) None of the mentioned

Answer: a

Explanation: Total pressure, F=w*a*y

=9.81*650*6*2*3

=22.9 N/cm 2 .

2. Find the total pressure on a circular plate of diameter 3 m immersed in a fluid of specific gravity 0.75 at a depth of 5 m from the surface on a planet having acceleration dueto gravity 7 m/s 2 .

a) 18.5 N/cm 2

b) 37 N/cm 2

c) 9.25 N/cm 2

d) None of the mentioned

Answer: a

Explanation: Total pressure, F=w*a*y

=7*750*π*1.5*1.5*5

=18.5 N/cm 2 .

3. A rectangular plate surface 3m wide and 5m deep lies in fluid of specific gravity .9 such that its plane makes an angle of 45⁰ with water surface, upper edge 3m below free water surface. Determine the total pressure.

a) 86.5 N/cm 2

b) 173 N/cm 2

c) 43.25 N/cm 2

d) None of the mentioned

Answer: a

Explanation: Total pressure, F=w*a*ŷ=w*A*=9.81*900*15*

=86.5 N/cm 2 .

4. A rectangular plan surface 5 m wide and 7 m deep lies in water in such a way that its plane makes an angle 60⁰ with the free surface of water. Determine the total pressure force when the upper edge is 3 m below the free surface.

a) 311.15 N/cm 2

b) 622.3 N/cm 2

c) 155.5 N/cm 2

d) None of the mentioned

Answer: a

Explanation: Total pressure, F=w*a*ŷ=w*A*=9.81*1000*35*=311.15 N/cm 2 .

5. A circular plate 5.0 m diameter is immersed in such a way that its greatest and least depth below the free surface are 3 m and 1 m respectively. determine the position of the centre of pressure.

a) 2.5 m

b) 5 m

c) 4.5 m

d) 6 m

Answer: a

Explanation: centre of pressure, ŷ=I*sin²θ/Aĥ + ĥ

…….ĥ=

=3.142*2.5 4 *sin²23.58/3.142*2.5 2 *+*

=2.5 m.

6. For an inclined plate the pressure intensity at every point differs.

a) True

b) False

Answer: a

Explanation: Due to inclination the depth of every point is different from the free liquid surface. Hence, the pressure intensity varies with depth.

7. The pressure intensity for a horizontal plate is maximum on the surface of the earth and decreases as we move further away from the surface of the earth either downward or upward.

a) True

b) False

Answer: a

Explanation: As we move away from the surface of the earth either downward or upward g decreases, w decreases. Hence pressure intensity decreases.

8. For an inclined plane for which position, maximum total pressure acts on it.

a) Horizontal

b) Vertical

c) Inclined

d) None of the mentioned

Answer: b

Explanation: Total pressure, F=w*a*ŷ=w*A*

For vertical plate, θ=90⁰

Hence, total pressure is maximum.

9. The total pressure or pressure intensity is zero for any point on inclined surface in space.

a) True

b) False

Answer: a

Explanation: Total pressure, F=w*a*ŷ

In space, w=0 as g=0

Hence, f=0.

10. In case of spherical bodies with uniform mass distribution, what is the position of center of pressure relative to centre of gravity.

a) Above

b) Below

c) Coincides

d) None of the mentioned

Answer: c

Explanation: In case of spherical bodies with uniform mass distribution, centre of pressure coincides with centre of gravity.

This set of Fluid Mechanics MCQs focuses on “Pressure Distribution in a Liquid Subjected to Horizontal / Vertical Acceleration”.

1. A rectangular tank is moving horizontally in the direction of its length with a constant acceleration of 3.6 m/s 2 . If tank is open at the top then calculate the angle of water surface to the horizontal.

a) 20.15

b) 69.84

c) 40.30

d) None of the mentioned

Answer: a

Explanation: tanθ=a/g

tanθ=3.6/9.8

θ=20.15⁰.

2. A rectangular tank is moving horizontally in the direction of its length with a constant acceleration of 4.8 m/s 2 . The length of tank is 7 m and depth is 1.5 m. If tank is open at the top then calculate the maximum pressure intensity at the bottom.

a) 6.3 N/cm 2

b) 3.15 N/cm 2

c) 12.6 N/cm 2

d) 1.6 N/cm 2

Answer: b

Explanation: tanθ=a/g

tanθ=4.8/9.8

θ=26.07⁰

h= d+tanθ

= 1.5+3.5tan26.07

= 3.21 m

p=ρ*g*h

=3.15 N/cm 2 .

3. A rectangular tank is moving horizontally in the direction of its length with a constant acceleration of 5.5 m/s 2 . The length of tank is 5.5 m and depth is 2 m. If tank is open at the top then calculate the minimum pressure intensity at the bottom.

a) 3.8 N/cm 2

b) 1.9 N/cm 2

c) 5.7 N/cm 2

d) 2.6 N/cm 2

Answer: b

Explanation: tanθ=a/g

tanθ=5.5/9.8

θ=29.28⁰

h= d-tanθ

= 2-2.75 tan29.28

= 3.21 m

p=ρ*g*h

=1.9 N/cm 2 .

4. A rectangular tank is moving horizontally in the direction of its length with a constant acceleration of 4.5 m/s2.The length, width and depth of tank are 7 m, 3m, 2.5m respectively. If tank is open at the top then calculate the total force due to water acting on higher pressure end of the tank.

a) 1.07 MN

b) 2.14 MN

c) 4.28 MN

d) 4.35 MN

Answer: a

Explanation: tanθ=a/g

tanθ=4.5/9.8

θ=24.64⁰

h= d+tanθ

= 2.5+3.5tan24.64

= 4.1 m

F=wAĥ

=9810*2.68*4.1

= 1.07 MN.

5. A tank containing water upto a depth of 500 mm is moving vertically upward with a constant acceleration of 2.45 m/s 2 . Find the force exerted by fluid of specific gravity .65 on the side of tank,width of tank is 1m.

a) 996.1 N

b) 1992.2 N

c) 498.06 N

d) 124.5 N

Answer: a

Explanation: p=ρ*g*h*

=650*9.81*0.5*

=3984.5 N/m 2

F=wAĥ

= 650*9.81*0.5*0.5*3984.5

= 996.1N.

6. A tank containing water upto a depth of 750 mm is moving vertically downward with a constant acceleration of 3.45 m/s 2 . Find the force exerted by fluid of specific gravity .85 on the side of tank,width of tank is 2m

a) 2682.75 N

b) 5365.5 N

c) 1341.25 N

d) 4024.5 N

Answer: a

Explanation: p=ρ*g*h*

=750*9.81*0.75*

=3577 N/m 2

F=wAĥ

= 0.5*0.75*3984.5*2

= 2682.75 N.

7. A tank containing water upto a depth of 650 mm is stationary. Find the force exerted by fluid of specific gravity .55 on the side of tank,width of tank is 1.5m

a) 1709.9 N

b) 3419.4N

c) 6838.8 N

d) 1367.75 N

Answer: a

Explanation: p=ρ*g*h

=550*9.81*0.65

=3507 N/m 2

F=wAĥ

= 0.5*0.65*3507*1.5

= 1709.7N.

8. The pressure intensity at the bottom remains same, even if the tank moves with constant horizontal acceleration.

a) True

b) False

Answer: b

Explanation: The pressure intensity at the bottom differs due to variation in height as tank moves with constant acceleration.

9. There will be development of shear stress due to the dynamic motion of tank or container.

a) True

b) False

Answer: b

Explanation: The water in tank is at rest even if the tank is moving.

10. If the tank is moving vertically, which of its component is subjected to maximum total pressure?

a) Lower part of vertical walls

b) Higher part of vertical walls

c) Base

d) None of the mentioned

Answer: c

Explanation: Base bores the direct pressure.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Manometer”.

1. In a stationary fluid, how does the local pressure of the fluid vary?

a) With depth only

b) In the horizontal direction only

c) Both with depth and along horizontal direction

d) Neither with depth nor along horizontal direction

Answer: a

Explanation: According to Pascal’s law, the local pressure of a fluid is same in all directions. Hence, the pressure won’t vary along the x and y direction. The local pressure will increase with an increase in depth due to the extra weight of water column above that point.

2. Which of the following cannot be the value of absolute pressure of a fluid at any point?

a) 0

b) 1.013 bar

c) – 1 bar

d) 200 bar

Answer: c

Explanation: Absolute zero pressure is the reference used for the measurement of absolute pressure. Absolute zero pressure is possible . Hence, 0 and positive values are possible, but a negative value is impossible.

3. A student wants to find the absolute pressure of water at a point below the surface of water. He has a barometer and a manometer pressure gauge. The barometer reads 1.3152 bar where as the manometer pressure gauge reads 0.3152 bar. What is the absolute pressure? 

a) 1 bar

b) 1.6304 bar

c) 0.3152 bar

d) 1.3152 bar

Answer: b

Explanation: The options may tempt you to subtract the readings, but the concept of barometer and manometer is important. Barometer measures the atmospheric pressure whereas, the manometer reads the gauge pressure. Hence, we need to add the two values.

4. In a U-tube manometer, one end is open to the atmosphere, the other end attached to a pressurized gas of gauge pressure 40 kPa. The height of the fluid column in the atmospheric side is 60 cm, and that on the gas side is 30 cm. The manometic fluid used is: (Take g = 9.8 m/s 2 ).

a) Water

b) Liquid ammonia

c) Oil

d) Mercury

Answer: d

Explanation: Gauge pressure = 40000 Pa. Height difference = 60 – 30 = 30 cm = 0.3 m. ρ*g*(h 2 – h 1 ) = 40000. We get, ρ = 13605 kg/m 3 = Density of mercury.

5. In a U-tube mercury manometer, one end is exposed to the atmosphere and the other end is connected to a pressurized gas. The gauge pressure of the gas is found to be 40 kPa. Now, we change the manometric fluid to water. The height difference changes by: (ρmercury = 13600 kg/m 3 , ρwater = 1000 kg/m 3 ).

a) 1260%

b) 92.64 %

c) Remains unchanged 

d) 13.6%

Answer: a

Explanation: Since the gauge pressure remains the same ρ*(h 2 – h 1 ) = constant. The height difference in mercury manometer is 0.30 m and that in a water manometer is 4.08 m. Percent change is thus, 1260%. Be careful about the denominator used for computing percent change.

6. A manometric liquid should suitably have _________

a) Low density & Low Vapour pressure

b) Low density & High Vapour pressure

c) High density & Low Vapour pressure

d) High density & High Vapour pressure

Answer: c

Explanation: A high density is favourable because the height of the column required for the manometer would be low. A liquid with high vapour pressure would be less sensitive to changes in pressure and may result in a slower rise of the manometric fluid. Thus, a fluid with low vapour pressure is favourable.

7. A simple U-tube manometer can measure negative gauge pressures.

a) True

b) False

Answer: a

Explanation: The height of the manometric fluid in a U-tube manometer in the test column would fall if there is a positive gauge pressure. The height would increase if there is a negative gauge pressure. It is possible to measure negative gauge pressures with a U-tube manometer. However, the negative pressure cannot fall below -1 Bar.

8. Both ends of a U-tube manometer are exposed to the atmosphere. There exists a possibility that the height difference of the manometer is non-zero. True or False?

a) True

b) False

Answer: a

Explanation: The height difference may be non-zero when there are multiple immiscible fluids used in the same manometer. Even though the pressure is same on both surfaces, the height would be different as the fluid with higher density will be at a lower height.

9.The below figure shows an inclined U-tube mercury manometer. The vertical end of the tube is exposed to a gas of gauge pressure 50 kPa and the inclined end is exposed to the atmosphere. The inclined part of the tube is at an angle of 30 o with the horizontal. Find the value of h  (take g = 9.8 m/s 2 , ρ mercury = 13600 kg/m 3 )

fluid-mechanics-questions-answers-manometer-q9

a) 60

b) 50

c) 75

d) 25

Answer: c

Explanation: Pressure along the dotted line will be 50 kPa. Gauge pressure in an inclined manometer is given by P = ρ.g.h.sin Ɵ. Substituting P, ρ and Ɵ, we get the value of h as 0.75 m.

10. In the manometer given above, 2 immiscible fluids mercury (ρ = 13600 kg/m 3 ) and water (ρ = 1000 kg/m 3 ) are used as manometric fluids. The water end is exposed to atmosphere  and the mercury end is exposed to a gas. At this position, the interface between the fluids is at the bottom most point of the manometer. Ignore the width of the manometer tube and the radius of curvature. The value of h is found to be 9.45 m. The height of the mercury column is given to be 75 cm. Find the gauge pressure of the gas. (g = 9.8 m/s 2 )

fluid-mechanics-questions-answers-manometer-q10

a) 100 kPa

b) 50 kPa

c) 200 kPa

d) 0 kPa

Answer: d

Explanation: Height of water column = 0.75 + 9.45 = 10.2 m. We equate the pressures at the bottom most point. P a + ρ w .g. = P g + ρ m .g.. We find, P g = 100 kPa = Absolute pressure. Hence, gauge pressure will be 0.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Bouyancy”.

1. Find the position of centre of buoyancy for a wooden block of width 3.5 m and depth 1 m, when it floats horizontally in water. The density of wooden block id 850 kg/m3 and its length 7.0 m.

a) 0.95

b) 0.85

c) 1.05

d) 1.65

Answer: b

Explanation: Weight of the block=ρ*g*Volume=850*9.81*7*3.5*1=204.29 kN

Volume of

water displaced= Weight of water displaced/weight density of water

= 20.825 m 3 .

h=20.825/3.5*7=0.85 m.

2. A stone weighs 450 N in air and 200 N in water. Compute the volume of stone.

a) .025 m 3

b) .05 m 3

c) .075 m 3

d) None of the mentioned

Answer: a

Explanation: Weight of water displaced=Weight of stone in air – Weight of stone in water

=250

Volume of water displaced=Volume of stone=250/9.81*1000=0.025 m 3 .

3. A stone weighs 650 N in air and 275 N in water. Compute its specific gravity.

a) 1.73

b) 2.45

c) 3.46

d) 0.865

Answer: a

Explanation: Weight of water displaced=Weight of stone in air – Weight of stone in water

=375

Volume of water displaced=Volume of stone=375/9.81*1000=0.038 m3

Density of stone= mass/volume=650/9.81*0.038=1733 kg/m 3

specific gravity= Density of stone/Density of water=1.73.

4. A body of dimensions 2.7 m * 3.8 m * 2.5 m, weighs 2500 N in water.Find its weight in air.

a) 254.12 kN

b) 508.25 kN

c) 101.65 kN

d) 127.06 kN

Answer: a

Explanation: Weight of stone in air = Weight of water displaced+Weight of stone in water

= 9.81*1000*2.7*3.8*2.5+2500=254.12 kN.

5. Find the density of metallic body which floats at the interface of mercury of sp.gr 13.6 and water such that 40 % of its volume is sub-merged in mercury and 60% in water.

a) 6040 kg/m 3

b) 12080 kg/m 3

c) 24160 kg/m 3

d) 3020 kg/m 3

Answer: a

Explanation: Total Bouyant force=Force of bouyancy due to water+Force of bouyancy due to mercury

For equilibrium, Total bouyant force= Weiht of body

1000*9.81*0.6*V + 13.6*1000*9.81*0.4*V=ρ*g*V

ρ=6040 kg/m 3 .

6. What is the principal cause of action of buoyant force on a body submerged partially or fully in fluid?

a) Displacement of fluid due to submerged body

b) Development of force due to dynamic action

c) Internal shear forces mitigating external forces

d) None of the mentioned

Answer: a

Explanation: The principal cause of action of buoyant force on a body submerged partially or fully in fluid is the force equal in magnitude to the weight of the volume of displaced fluid.

7. How can relatively denser object be made to float on the less dense fluid?

a) By altering the shape.

b) By altering the forces acting on the object

c) By altering the shear forces acting on the object

d) None of the mentioned

Answer: a

Explanation: By changing the shape of an object it can be made to float on a fluid even if it is denser than that fluid. This principle is used in ship building.

8. What happens to the buoyant force acting on the airship as it rises in the air?

a) Buoyant force increases

b) Buoyant force decreases

c) Buoyant force remains constant

d) Buoyant force first increases then shows decrease

Answer: b

Explanation: Buoyant force acting on the airship decreases as it rises in the air as air at higher altitude becomes rarer and its density decreases.

9. As a balloon rises in the air its volume increases, at the end it acquires a stable height and cannot rise any further.

a) True

b) False

Answer: a

Explanation: As balloon rises in air, pressure acting on it reduces and therefore its volume increases. Also, a rising balloon ceases rising when it and the displaced air are equal in weight.

10. Submarines use principle of ‘neutral buoyancy’ to go into the water.

a) True

b) False

Answer: a

Explanation: To dive, the submarine tanks are opened to allow air to exhaust, while the water flows in. When the weight has been balanced so the overall density of the submarine is equal to the water around it, it has neutral buoyancy and hence will go down.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Metacentre and Metacentric Height”.

1. A rectangular pontoon is 5 m long, 3 m wide and 1.40 m high. The depth of immersion of the pontoon is 0.60 m in seawater. If the centre of gravity is 0.7 m above the bottom of the pontoon, determine the metacentric height. The density for seawater = 1045 kg/m 3 .

a) 0.135

b) 0.271

c) 0.543

d) 0.068

Answer: a

Explanation: BG=Centre of pontoon – Centre of immersed portion=0.7-0.3=0.4

Metacentric height=I/∀ -BG

I=bd³/12 = 5*3³/12

∀=5*3*1.4

Metacentric height=0.135 m.

2. A uniform body of size 4 m long * 2.5 m wide * 1.5 m deep floats in water. What is the weight of the body if depth of immersion is 1 m ?

a) 147.1 kN

b) 294.3 kN

c) 73.5 kN

d) 588.6 kN

Answer: a

Explanation: Weight of Body = Weight of water displaced

= ρ*g*Volume of displaced water=9.81*1000*4*2.5*1.5=147.1kN.

3. A block of material of specific gravity 0.45 floats in water. Determine the meta-centric height of the block if its size is 3 m * 2 m* 0.8 m.

a) 0.506 m

b) 0.376 m

c) 1.012 m

d) 0.127 m

Answer: b

Explanation: BG= Centre of pontoon – Centre of immersed portion=0.4 – 0.55*0.8=0.04

Metacentric height=I/∀ -BG

I=bd³/12 = 3*2³/12

∀=3*2*0.8

Metacentric height=0.376 m.

4. A solid cylinder of diameter 4.5 has a height of 2.5 metres. Find the meta-centric height of the cylinder when it is floating in water with its axis vertical. The sp. gr. of the cylinder=0.45.

a) 1.9 m

b) 3.8 m

c) 5.7 m

d) .95 m

Answer: a

Explanation:BG= Centre of pontoon – Centre of immersed portion=1.25-0.45*2.5=0.125

Metacentric height=I/∀ -BG

I=π*r⁴

∀= π*r*r*h

Metacentric height=1.9 m.

5. In case of spherically shaped bodies of uniform mass distribution and completely immersed in fluid and floating, the centre of buoyancy coincides with centre of gravity.

a) True

b) False

Answer: a

Explanation: The volume of fluid displaced by the body is equal to the actual volume of body in air. Hence, In case of spherically shaped bodies of uniform mass distribution and completely immersed in fluid and floating, the centre of buoyancy coincides with centre of gravity.

6. Proper explanation for metacentre is:

a) Point at which line of action of force meets the normal axis of body when it is given angular displacement

b) Intersection of line passing through new centre of buoyancy and centre of gravity.

c) point about which body starts oscillating when it is given small angular displacement

d) All of the mentioned

Answer: d

Explanation: All of the above explanation are apt.

7. The metacentric height is affected by the change in density.

a) True

b) False

Answer: True

Explanation: Metacentre does depend on the density. Hence, the metacentric height is affected by the change in density.

8.For a completely immersed body, the metacentric height is always zero.

a) True

b) False

Answer: b

Explanation: The metacentric height may or may not be zero as metacentre will not always coincide with centre of gravity.

9. Meta centre always lies below the centre of gravity

a) True

b) False

Answer: b

Explanation: It depends on the stability of floating body.

10. The principle of floatation of bodies is based on the premise of

a) Metacentre

b) Newtons first law

c) Newtons law of viscosity

d) None of the mentioned

Answer: a

Explanation: The principle of floatation of bodies is based on the premise of Metacentre.

This set of Fluid Mechanics Multiple Choice Questions & Answers focuses on “Conditions of Equilibrium of a Floating and Submerged Bodies”.

1. A solid cylinder of diameter 5.0 m has a height of 6.0 m. Find the meta-centric height of the cylinder if the specific gravity of the material of cylinder 0.45 and it is floating in water with its axis vertical. State whether the equilibrium is stable or unstable.

a) -0.29 m

b) -0.61 m

c) -1.16 m

d) 0.14 m

Answer: b

Explanation: BG=Centre of pontoon – Centre of immersed portion=0.3-0.45*0.3=1.65

Metacentric height=I/∀ -BG

I=π*r⁴=π*2.5⁴

∀=π*r*r*h=π*2.5*2.5*6

Metacentric height=-0.61.

2. A solid cylinder of 15 cm diameter and 40 cm long, consists of two parts made of different materials. The first part at the base is 1.5 cm long and of specific gravity=6.5. The other part of the cylinder is made of the material having specific gravity 0.75. State, if the it can float vertically in water.

a) It will float

b) It will not float

c) Data insufficient

d) None of the mentioned

Answer: a

Explanation: AG= + / )weight of base + weight of upper part)

= 14.52

By principle of buoyancy,

Weight of cylinder = Weight of water displaced

h=38.625

AB=19.31

BG=14.25-19.31= -4.79

GM= Metacentric height=I/∀ -BG

= 6.16

As metacentric height is positive, it will float.

3. A wooden cylinder of sp.gr. = 0.6 and circular in cross-section is required to float in oil. Find the L/D ratio for the cylinder to float with its longitudinal axis vertical in oil, where L is the height of cylinder and D is its diameter.

a) L/D<9/16

b) L/D<3/4

c) L/D<2/3

d) None of the mentioned

Answer: b

Explanation: By principle of buoyancy,

Weight of cylinder = Weight of water displaced

h=2L/3

AG=L/2

AB=L/3

BG=AG-AB=L/6

GM= Metacentric height=I/∀ – BG=3D2/32L-L/6

For stable equilibrium, GM should be positive

GM>0

i.e L/D<3/4.

4. A cylinder of radius 3.0 m has a height of 9.0 m. The specific gravity of the material of cylinder 0.85 and it is floating in water with its axis vertical. State whether the equilibrium is stable or unstable.

a) Stable

b) Unstable

c) Insufficient Data

d) None of the mentioned

Answer: a

Explanation: BG=Centre of pontoon – Centre of immersed portion=0.3-0.45*0.3=1.65

Metacentric height=I/∀ -BG

I=π*r⁴=π*3⁴

∀=π*r*r*h=π*3*3*9

Metacentric height=0.325.

5. If the magnitude of dimension of a rectangular wooden block is length>breadth>height, then for it to float on the water, it should be immersed in what manner?

a) It should be immersed vertically such that length is partially immersed

b) It should be immersed horizontally such that breadth is partially immersed

c) It should be immersed such that height is partially immersed

d) None of the mentioned

Answer: b

Explanation: When it is immersed in such a manner where height is partially immersed, its stability is most as moment of inertia is most about that axis.

6. When body is completely or partially immersed in a fluid, how much its weight be distributed for it to be in stable equilibrium.

a) Around the lower part

b) Around the upper part

c) Is independent of weight distribution

d) None of the mentioned

Answer: a

Explanation: When the weight distribution is around the lower part, the centre of gravity is at lower portion and hence below the centre of buoyancy which is condition for stable equilibrium.

7. In unstable equilibrium what is the relation between forces?

a) Buoyancy force= Weight of body

b) Buoyancy force > Weight of body

c) Buoyancy force < Weight of body

d) None of the mentioned

Answer: a

Explanation: Fb=W and the the centre of buoyancy is below the centre of gravity.

8. The floating body is said to be in unstable equilibrium if the metacentre is below the centre of gravity.

a) True

b) False

Answer: b

Explanation: The floating body is said to be in unstable equilibrium if the metacentre is above the centre of gravity.

9. The floating body is said to be in neutraL equilibrium if the metacentre is above the centre of gravity.

a) True

b) False

Answer: b

Explanation: The floating body is said to be in unstable equilibrium if the metacentre coincides with the centre of gravity.

10. In stable equilibrium for completely submerged bodies what is the relation between forces?

a) Buoyancy force= Weight of body,the centre of buoyancy is below the centre of gravity.

b) Buoyancy force=Weight of body, the centre of buoyancy is above the centre of gravity.

c) Buoyancy force < Weight of body

d) None of the mentioned

Answer: b

Explanation: Fb=W and the the centre of buoyancy is above the centre of gravity.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Types of Fluid Flow”.

1. Which method is used exclusively in fluid mechanics?

a) Lagrangian method

b) Eulerian method

c) Both Lagrangian and Eulerian methods

d) Neither Lagrangian nor Eulerian method

Answer: b

Explanation: In Fluid Mechanics, the matter of concern is the general state of motion at various points in the fluid system  rather than the motion of each particle . Hence, the Eulerian method is extensively used in Fluid Mechanics.

2. A beaker contains water up to a certain height as shown. If the water is allowed to get discharged through a small pipe , what type of flow will it be in the pipe?

fluid-mechanics-questions-answers-types-fluid-flow-q2

a) steady and uniform

b) unsteady and uniform

c) steady and non-uniform

d) unsteady and non-uniform

Answer: b

Explanation: The velocity in which the water is discharged with a velocity  With time as the water gets discharged,v decreases as H decreases. Hence, it will be an unsteady flow.

According to the continuity equation, ρAV =constant, where ρ= density, A= cross-sectional area of flow, V = velocity of flow. Since water is treated as an incompressible liquid  and the pipe has a uniform diameter  at a given instant, V will remain constant throughout the whole cross-section of the pipe. Hence, it will be a uniform flow.

3. A beaker contains water up to a certain height as shown. If the water is allowed to get discharged through a small nozzle, what type of flow will it be in the pipe?

a) steady and uniform

b) unsteady and uniform

c) steady and non-uniform

d) unsteady and non-uniform

Answer: d

Explanation: The velocity in which the water is discharged with a velocity  With time as the water gets discharged,v decreases as H decreases. Hence, it will be an unsteady flow.

According to the continuity equation, ρAV =constant, where ρ= density, A= cross-sectional area of flow, V = velocity of flow. In this case, water is treated as an incompressible liquid  but the nozzle has a gradually decreasing diameter . At a given instant, V at the exit of the nozzle will be more than that at it’s entrance. Hence, it will be a non-uniform flow.

4. A beaker contains water up to a certain height as shown. If the water is allowed to get discharged through a small diffuser, what type of flow will it be in the pipe?

a) steady and uniform

b) unsteady and uniform

c) steady and non-uniform

d) unsteady and non-uniform

Answer: d

Explanation: The velocity in which the water is discharged with a velocity  With time as the water gets discharged,v decreases as H decreases. Hence, it will be an unsteady flow.

According to the continuity equation, ρAV =constant, where ρ= density, A= cross-sectional area of flow, V = velocity of flow. In this case, water is treated as an incompressible liquid  but the nozzle has a gradually increasing diameter . At a given instant, V at the exit of the nozzle will be less than that at it’s entrance. Hence, it will be a non-uniform flow.

5. What type of flow can be taken for granted in a pipe of a uniform cross-section?

a) steady

b) unsteady

c) uniform

d) non-uniform

Answer: c

Explanation: According to the continuity equation, ρAV =constant, where ρ= density, A= cross-sectional area of flow, V = velocity of flow. For a pipe of a uniform cross-section, no matter what the rate of flow is, the velocity of flow inside the pipe will always remain constant. Hence, it’ll always be a uniform flow. It’ll be a steady flow if and only if the water level is maintained at a constant level by supplying water at the same rate as it gets discharged, else the water level will keep decreasing with time leading to an unsteady flow.

6. Can the flow inside a nozzle be steady and uniform?

a) yes

b) never

c) it can be steady but never uniform

d) it can be uniform but never steady

Answer: c

Explanation: According to the continuity equation, ρAV =constant, where ρ= density, A= cross-sectional area of flow, V = velocity of flow. For a nozzle, the area gradually decreases towards it’s exit. Thus, no matter what the rate of flow is, the velocity of flow at the nozzle exit will always be greater than that at it’s entrance. Hence, it’ll always be an unsteady flow. It can be a steady flow if and only if the water level is maintained at a constant level by supplying water at the same rate as it gets discharged, else the water level will keep decreasing with time leading to an unsteady flow.

7. Which of the following statements is true regarding one and two-dimensional flows?

a) Flow in a pipe is always taken as one-dimensional flow

b) Flow in a pipe is always taken as two-dimensional flow

c) Flow in a pipe is taken as one-dimensional flow when average flow parameters are considered

d) Flow in a pipe is taken as two-dimensional flow when average flow parameters are considered

Answer: c

Explanation: The flow inside a pipe can be described by the cylindrical co-ordinate system , where r is in the radial direction, θ in the angular direction and z in the axial direction. For a circular cross-sections, the flow can be taken to be independent of θ. Hence, it can be taken aa a two-dimensional flow. Again if aerage flow parameters are considered to account for the variation in the radial direction, the flow can be taken as an one-dimensional flow.

8. Which of the following is true?

a) Flow is rotational inside the boundary layer and irrotational outside

b) Flow is irrotational inside the boundary layer and rotational outside

c) Flow is rotational both inside and outside of the boundary layer

d) Flow is irrotational both inside and outside of the boundary layer

Answer: a

Explanation: When a torque is applied to a fluid particle, it undergoes a rotation. Thus, the rotation of a fluid particle will alwayds be associated with shear stress. Shear stress is in turn dependent on the viscosity. Hence, rotational flow occurs where the viscosity effects are predominant. Since, viscosity effects are predominant inside the blundary layer, the flow will be rotational in this region. However, outside the boundary layer, the viscosity effects are negligible. Hence, flow can be treated as irrotational outside the boundary layer.

9. Which of the following is true?

a) Flow is laminar inside the boundary layer and turbulent outside

b) Flow is turbulent inside the boundary layer and laminar outside

c) Flow is laminar both inside and outside of the boundary layer

d) Flow is turbulent both inside and outside of the boundary layer

Answer: a

Explanation: Flows can be characterized as laminar or turbulent on the basis of Reynold’s number Re = ρvd / μ, where ρ is the density, d is the pipe diameter and μ is the viscosity. For Re < 2000, the flow will be laminar and Re > 4000, the ow will be turbulent. For laminar flow, the viscosity effects must be high  as inside the boundary layer. Outside the boundary layer, the viscosity effects are negligible. Hence, the flow will be turbulent.

10. “The velocity of entrance and exit through a nozzle remains the same.” Is this ever possible?

a) only if the flow is compressible

b) only if the flow is laminar

c) only if the flow is rotational

d) never possible

Answer: a

Explanation: According to the continuity equation, ρAV =constant, where ρ= density, A= cross sectional area of flow, V = velocity of flow. If v =constant, ρA =constant. Thus a change is A will mean a change in ρ. Hence, the flow is possible only if the fluid is compressible.

11. Three flows named as 1,2 and 3 are observed. The Reynold’s number for the three are 100, 1000 and 10000. Which of the flows will be laminar?

a) only 1

b) only 1 and 2

c) 1, 2 and 3

d) only 3

Answer: b

Explanation: Flows can be characterized as laminar or turbulent on the basis of Reynold’s number Re = ρvd / μ, where ρ is the density, d is the pipe diameter and μ is the viscosity. For Re < 2000, the flow will be laminar and Re > 4000, the flow will be turbulent. Thus, flow 1 and 2 will be laminar.

12. Three flows named as 1,2 and 3 are observed. The flow velocities are v1 and v2. If all other geometrical factors remain the same along with the fluid considered, flow is more likely to be laminar?

a) flow 1 if v1 > v2

b) flow 2 if v1 > v2

c) always flow 1

d) always flow 2

Answer:

Explanation: Flows can be characterized as laminar or turbulent on the basis of Reynold’s number Re = ρvd / μ, where ρ is the density, d is the pipe diameter and μ is the viscosity. If all other geometrical factors remain the same along with the fluid considered, v1 > v2 implies Re1 > Re2. Thus, flow 2 is more likely to be laminar.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Types of Flow Lines”.

1. What will be the shape of the pathline for an one-dimensional flow be like?

a) straight line

b) parabolic

c) hyperbolic

d) elliptical

Answer: a

Explanation: A pathline is the path followed by a particle in motion. For an one-dimensional flow, the fluids move in only one dimension . Hence the pathline will also be a straight line .

2. Which of the following is correct?

a) Pathlines of two particles in an one-dimensional flow can never intersect

b) Pathlines of two particles in an one-dimensional flow can never intersect if the two particles move along the same direction

c) Pathlines of two particles in an one-dimensional flow can intersect only if the two particles move along the same direction

d) Pathlines of two particles in an one-dimensional flow can intersect only if the two particles move along different directions

Answer: c

Explanation: The pathline of a particle in an one-dimensional flow is a straight line along the direction it moves. If the two particles move along the same direction, their pathlines will be parallel to each other and will never intersect.

3. What is the maximum number of times the pathlines of two particles can intersect in an one dimensional flow?

a) 0

b) 1

c) 2

d) infinite

Answer: b

Explanation: The pathline of a particle in an one-dimensional flow is a straight line along the direction it moves. When two particles move in the same direction, their pathline will never intersect and when they move in different directions, their pathlines will intersect only once.

4. The velocity of a point in a flow is

a) along the streamline

b) tangent to the streamline

c) along the pathline

d) tangent to the pathline

Answer: b

Explanation: A pathline is the path followed by a particle in motion whereas a streamline is an imaginary line within the flow such that the tangent at any point on it indicates the velocity at that point.

5. Which of the following is correct?

a) A streamline can intersect itself and two streamlines can cross

b) A streamline cannot intersect itself but two streamlines can cross

c) A streamline can intersect itself but two streamlines cannot cross

d) A streamline cannot intersect itself and two streamlines cannot cross

Answer: d

Explanation: A streamline is defined as an imaginary line within the flow such that the tangent at any point on it indicates the velocity at that point. At a point, there can only be one direction of velocity. Hence, neither can a streamline intersect itself nor can two streamlines cross each other.

6. If three sets of streamlines A, B and C are considered across section 1-2, which set will represent accelerated flow from 1 to 2?

fluid-mechanics-questions-answers-types-flow-lines-q3

a) A

b) B

c) C

d) None of the sets

Answer: a

Explanation: Streamline spacing varies inversely as the velocity. Higher the velocity, closer will be the streamlines. Hence, converging of streamlines from 1 to 2 will indicate accelerated flow as in set A.

7. The streamlines of the particles in a flow are recorded. If the streamline distribution remain the same even after sometime, what type of flow can it be?

a) steady

b) unsteady

c) uniform

d) non-uniform

Answer: a

Explanation: A streamline is defined as an imaginary line within the flow such that the tangent at any point on it indicates the velocity at that point. In a steady flow, the velocity of the particles is constant with time. Hence, the streamlines remain the same even after sometime.

8. If the streamlines of the particles in a flow are parallel to each other, what type of flow can it be?

a) steady

b) unsteady

c) uniform

d) non-uniform

Answer: c

Explanation: Streamline spacing varies inversely as the velocity. In a uniform flow, the velocities of the particles are the same at every instant of time. Hence, the spacing between their streamlines will be the same. In other words, the streamlines will be parallel.

9. Which of the following is correct?

a) the movement of fluid mass can either be along the streamlines or across them

b) the movement of fluid mass can be along the streamlines but never across them

c) the movement of fluid mass can never be along the streamlines but can be across them

d) the movement of fluid mass can neither be along the streamlines or across them

Answer: b

Explanation: A streamline is defined as an imaginary line within the flow such that the tangent at any point on it indicates the velocity at that point. Flow can only be along the velocity, never perpendicular to it. Hence, the movement of fluid mass can only be along the streamlines and never across them.

10. Which of the following is correct?

a) pathlines are concerned with a number of particles at the same instant and streamlines with a particular particle at successive instants of time

b) pathlines are concerned with a particular particle at successive instants of time and streamlines with a number of particles at the same instant

c) both pathlines and streamlines are concerned with a number of particles at the same instant

d) both pathlines and streamlines are concerned with a particular particle at successive instants of time

Answer: b

Explanation: A pathline is the path followed by a particle in motion whereas a streamline is an imaginary line within the flow such that the tangent at any point on it indicates the velocity at that point. Thus, pathlines are concerned with a particular particle at successive instants of time and streamlines with a number of particles at the same instant.

11. The path taken by the smoke coming out of a chimney  represents a

a) pathline

b) streamline

c) streakline

d) streamtube

Answer: c

Explanation: A pathline is the path followed by a particle in motion whereas a streamline is an imaginary line within the flow such that the tangent at any point on it indicates the velocity at that point. A streamtube is a collection of streamlines. A streakline is a curve which gives an instantaneous picture of the location of the fluid particleswhich have passed through a given point.

Hence, the path taken by the smoke coming out of a chimney  will represent streaklines.

12. Which of the following is correct?

a) In steady flow, pathlines and streamlines are identical

b) In steady flow, pathlines and streaklines are identical

c) In steady flow, streaklines and streamlines are identical

d) In steady flow, pathline, streamlines and streaklines are all identical

Answer: d

Explanation: In case of a steady flow, the velocity at a point remains constant with time. Thus, there will be no geometrical distinction between the pathlines, streamlines and streaklines.

13. Which of the following is correct?

a) There will be no flow across the streamtube

b) There will be no flow along the streamtube

c) There will be no flow both across the streamtube and along it

d) There will be flow both across the streamtube and along it

Answer: a

Explanation: Streamtube is a fluid mass bounded by a group of streamlines. Since, the movement of the fluid mass can only be along the streamlines and never across them, there will be no flow across the streamtube.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Continuity Equation”.

1. If a liquid enters a pipe of diameter d with a velocity v, what will it’s velocity at the exit if the diameter reduces to 0.5d?

a) v

b) 0.5v

c) 2v

d) 4v

Answer: d

Explanation: According to the Continuity Equation,

where a represents flow area, v represents flow velocity, i is for inlet conditions and o is for outlet conditions.

fluid-mechanics-questions-answers-continuity-equation-q1a

2. The continuity equation is based on the principle of

a) conservation of mass

b) conservation of momentum

c) conservation of energy

d) conservation of force

Answer: a

Explanation: According to the Continuity Equation, if no fluid is added or removed from the pipe in any length then the mass passing across different sections shall be the same. This is in accordance with the principle of conservation of mass which states that matter can neither be created nor be destroyed.

3. Two pipes of diameters d1 and d2 converge to form a pipe of diameter d. If the liquid flows with a velocity of v1 and v2 in the two pipes, what will be the flow velocity in the third pipe?

fluid-mechanics-questions-answers-continuity-equation-q3

Answer: d

Explanation: According to the Continuity Equation,

where a represents flow area, v represents flow velocity, i is for inlet conditions and o is for outlet conditions. Thus,

fluid-mechanics-questions-answers-continuity-equation-q2a

4. Two pipes of diameters d1 and d2 converge to form a pipe of diameter 2d. If the liquid flows with a velocity of v1 and v2 in the two pipes, what will be the flow velocity in the third pipe?

a) v1 + v2

b) v1 + v2/2

c) v1 + v2/4

d) 2

Answer: c

Explanation: According to the Continuity Equation,

where a represents flow area, v represents flow velocity, i is for inlet conditions and o is for outlet conditions. Thus,

fluid-mechanics-questions-answers-continuity-equation-q4a

5. Two pipes, each of diameter d, converge to form a pipe of diameter D. What should be the relation between d and D such that the flow velocity in the third pipe becomes double of that in each of the two pipes?

a) D = d

b) D = 2d

c) D = 3d

d) D = 4d

Answer: a

Explanation: According to the Continuity Equation,

fluid-mechanics-questions-answers-continuity-equation-q5

where a represents flow area, v represents flow velocity, i is for inlet conditions and o is for outlet conditions. Thus,

A 1 v 1 + A 2 v 2 = Av

d 2 v + d 2 v = D 2 v

D = d.

6. Two pipes, each of diameter d, converge to form a pipe of diameter D. What should be the

relation between d and D such that the

ow velocity in the third pipe becomes half of that in each

of the two pipes?

a) D = d/2

b) D = d/3

c) D = d/4

d) D = d/5

Answer: a

Explanation: According to the Continuity Equation,

fluid-mechanics-questions-answers-continuity-equation-q5

where a represents flow area, v represents flow velocity, i is for inlet conditions and o is for outlet conditions. Thus,

A 1 v 1 + A 2 v 2 = Av

d 2 v + d 2 v = D v/2

d = D ⁄ 4.

7. In a two dimensional flow, the component of the velocity along the X-axis is u = ax 2 + bxy + cy 2 .

If v = 0 at y = 0, what will be the velocity component in the Y-direction?

a) v = 2axy + by 2

b) v = 2axy + b ⁄ 2 y 2

c) v = -2axy – b ⁄ 2 y 2

d) v = -axy – b ⁄ 2 y 2

Answer: c

Explanation: According to the condition for continuity,

fluid-mechanics-questions-answers-continuity-equation-q7

8. In a two dimensional flow, the component of the velocity along the X-axis and the Y-axis are u = ax 2 + bxy + cy 2 and v = cxy. What should be the condition for the flow field to be continuous?

a) a + c = 0

b) b + c = 0

c) 2a + c = 0

d) 2b + c = 0

Answer: c

Explanation: According to the condition for continuity,

2ax + cx = 0

2a + c = 0.

9. In a two dimensional flow, the component of the velocity along the X-axis and the Y-axis are u = axy and v = bx 2 + cy 2 . What should be the condition for the flow field to be continuous?

a) a + b = 0

b) a + c = 0

c) a + 2b = 0

d) a + 2c = 0

Answer: d

Explanation: The condition for the flow field to be continuous is:

ay + 2cy = 0

a + 2c = 0.

10. In a two dimensional flow, the component of the velocity along the X-axis and the Y-axis are u = ax 2 + bxy and v = cxy +dy 2 . What should be the condition for the flow field to be continuous?

a) x + y = 0

b) x + y = 0

c) x + y = 0

d) x + y = 0

Answer: d

Explanation: The condition for the flow field to be continuous is:

2ax + cx + by + 2dy = 0

x + y = 0.

11. In a two dimensional flow, the component of the velocity along the X-axis and the Y-axis are u = ax 2 + bxy and v = bxy + ay 2 . The condition for the flow field to be continuous is

a) independent of the constants  but dependent on the variables 

b) independent of the variables  but dependent on the constants 

c) independent of both the constants  and the variables 

d) dependent on both the constants  and the variables 

Answer: a

Explanation: The condition for the flow field to be continuous is:

2ax + by + 2ay + bx = 0

x + y = 0

Hence, the condition for the flow field to be continuous is independent of the constants  and dependent only on the variables .

12. In a two dimensional flow, the component of the velocity along the X-axis and the Y-axis are u = ax + by and v = ax – by. For what condition will the flow field be continuous?

a) impossible

b) possible if a = b

c) possible if a = 2b

d) possible for all values of a and b

Answer: d

Explanation: The condition for the flow field to be continuous is:

fluid-mechanics-questions-answers-continuity-equation-q12

Thus, the condition will be satisfied for any and every value of a and b.

13. In a two dimensional flow, the component of the velocity along the X-axis and the Y-axis are u = ay 2 + bxy and v = ax 2 + bxy. The flow will be continuous if

a) a + b = 0

b) a – b = 0

c) x + y = 0

d) x – y = 0

Answer: c

Explanation: The condition for the flow field to be continuous is:

by + bx = 0

x + y = 0.

14. In a two dimensional flow, the component of the velocity along the X-axis and the Y-axis are u = ax 2 + bxy and v = bxy + ay 2 . The condition for the flow field to be continuous is

a) independent of a and b

b) independent of a and c

c) independent of b and c

d) independent of a, b and c

Answer: d

Explanation: The condition for the flow field to be continuous is:

2ax + by + 2ay + bx = 0

x + y = 0

Hence, the condition for the flow field to be continuous is independent of a, b and c.

15. In a water supply system, water flows in from pipes 1 and 2 and goes out from pipes 3 and 4 as shown. If all the pipes have the same diameter, which of the following must be correct?

fluid-mechanics-questions-answers-continuity-equation-q15

a) the sum of the flow velocities in 1 and 2 is equal to that in 3 and 4

b) the sum of the flow velocities in 1 and 3 is equal to that in 2 and 4

c) the sum of the flow velocities in 1 and 4 is equal to that in 2 and 3

d) the flow velocities in 1 and 2 is equal to that in 3 and 4

Answer: a

Explanation: According to the Continuity Equation,

where a represents flow area, v represents flow velocity, i is for inlet conditions and o is for outlet conditions.

A 1 v 1 + A 2 v 2 = A 3 v 3 + A 4 v 4

Since d 1 = d 2 = d 3 = d 4 , v 1 + v 2 = v 3 + v 4 .

This set of Basic Fluid Mechanics Questions and Answers focuses on “Fluid Flow Methods and Types”.

1. In which method of fluid flow analysis do we describe the motion parameters at a point?

a) Langragian method

b) Eulerian Method

c) Control volume analysis

d) None of the mentioned

Answer: b

Explanation: In Eulerian method,we describe velocity, acceleration pressure etc at a point in flow field.

2. Which method is most commonly used in fluid mechanics for analysis?

a) Langragian method

b) Eulerian Method

c) Control volume analysis

d) None of the mentioned

Answer: b

Explanation: In Eulerian method,we describe velocity, acceleration pressure etc at a point in flow field.hence, it is also most commonly used in fluid mechanics.

3.In unsteady flow, the flow parameters change with respect to position.

a) True

b) False

Answer: b

Explanation: In unsteady flow, the flow parameters change with respect to time.

4. Uniform flow is defined as the type of flow in which acceleration is zero i.e velocity is constant.

a) True

b) False

Answer: b

Explanation: Uniform flow is defined as the type of flow in which the velocity does not change with respect to space. It can change with respect to time.

5. In laminar flow fluid particles flow along a streamline.

a) True

b) False

Answer: a

Explanation: As per the definition of laminar flow, fluid particles flow in a streamlined manner.

6. Eddies formed in the turbulent flow are major cause of the energy loss in the turbulent flow.

a) True

b) False

Answer: a

Explanation: Due to zig zag motion of particles eddies are formed and they lead to energy losses.

7. For compressible flow specific gravity remains same.

a) True

b) False

Answer: b

Explanation: For compressible flow, density changes and therefore specific gravity changes.

8. When the flow particles flow in zigzag manner and rotate about their own axis it is what type of flow?

a) Turbulent flow

b) Irrotational flow

c) Rotational flow

d) None of the mentioned

Answer: d

Explanation: It is random manner of fluid flow.

9. If the velocity is function of two space coordinates along with time then fluid flow is three dimensional in nature.

a) True

b) False

Answer: a

Explanation: If the velocity is function of three space coordinates along with time then fluid flow is three dimensional in nature.

10. What is unit for flow rate for gases?

a) m 3 /s

b) litres/s

c) cm 3 /s

d) kgf/s

Answer: d

Explanation: Unit for flow rate for gases is Newtons/s or kgf/s.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Continuity Equation in Two and Three Dimensions”.

1. The continuity equation is based on the premise of-

a) Law of conservation of energy

b) Law of conservation of mass

c) Law of conservation of momentum

d) None of the mentioned

Answer: b

Explanation: Continuity equation is based on the the principle of conservation of mass.

2. The continuity equation is only applicable to incompressible fluid.

a) True

b) False

Answer: b

Explanation: The continuity equation is only applicable to incompressible as well as compressible fluid.

3. For incompressible fluid flow, if area reduces then what is the effect on the velocity.

a) increases

b) decreases

c) first increases then decreases

d) first decreases then increases

Answer: a

Explanation: According to continuity equation,

Area × velocity = constant

Hence, as area decreases velocity increases.

4. For compressible fluid flow in a pipe, having decrease in specific gravity what will be the effect of decrease in diameter?

a) It will cause increase in velocity

b) It will cause decrease in velocity

c) It remains constant

d) None of the mentioned

Answer: a

Explanation: According to continuity equation,

ρ*A*v = constant

Hence, as density and area decreases velocity is bound to increase.

5. What is the most common assumption while dealing with fluid flow problems using continuity equation?

a) Flow is assumed to be compressible

b) Flow is assumed to be unsteady

c) Flow is assumed to be steady

d) Flow is assumed to be turbulent

Answer: c

Explanation: In majority of the fluid flow problems, flow is assumed to be steady.

6. The diameters of a pipe at the sections 1 and 2 are 8 cm and 13 cm respectively. Find the discharge through pipe if the velocity of water flowing through the pipe at section 1 is 6 m/s. Determine also the velocity at section 2.

a) 2.27 m/s

b) 4.54 m/s

c) 1.13 m/s

d) 3.25 m/s

Answer: a

Explanation: According to continuity equation,

Area × velocity = constant

Area1*Velocity1 = Area2*Velocity2

Velocity2=/Area2

= (8 2 * 6) / 13 2 =2.27 m/s.

7. The continuity equation can only be used for analysis of conserved quantity.

a) True

b) False

Answer: a

Explanation: Continuity equation is defined on a control volume and hence, is applicable only to Conserved quantities.

8. The diameter of a pipe at the section 1 is 9 cm. If the velocity of water flowing through the pipe at section 1 is 4.8 m/s and section 2 is 9 m/s, Determine the area at section 2.

a) 33.93 m 2

b) 67.86 m 2

c) 16.96 m 2

d) 38.66 m 2

Answer: a

Explanation: According to continuity equation,

Area × velocity = constant

Area1*Velocity1 = Area2*Velocity2

/Velocity2=Area2

Area 2= 33.93 m 2 .

9. For a flow to be physically possible it must primarily satisfy which equation?

a) Equation of conservation of energy

b) Equation of conservation of mass or continuity equation

c) Equation of conservation of momentum

d) None of the mentioned

Answer: a

Explanation: Fluid flow must satisfy equation of conservation of mass or continuity equation, for itto be physically possible.

10. Continuity equation can also be derived for polar coordinate system

a) True

b) False

Answer: a

Explanation: Continuity equation in polar coordinate is also used for analysis.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Velocity and Acceleration”.

1. The velocity vector in a fluid is given V=5x 4 +3y 2 +2z. What is the acceleration of it at point  ?

a) 40 m/s 2

b) 20 m/s 2

c) 60 m/s 2

d) 80 m/s 2

Answer: a

Explanation: By differentiating V=5x 4 2+2z, the acceleration obtained is V=20x 3 +6y+2.

on putting the coordinates, the acceleration obtained is 40 m/s 2 .

2. Determine the third velocity component such that continuity equation is satisfied if two components are u=2y 2 , w=2xyz.

a) -2xy+x 2 y+f

b) 4xy-x 2 y+f

c) -4xy-x 2 y+f

d) -2xy-x 2 y+f

Answer: c

Explanation: The continuity equation for incompressible is du/dx+dv/dy+dw/dz = 0.

Here du/dx=0 and w=2xy.

On solving by integrating, we get v = -4xy-x 2 y+f.

3. Determine the third velocity component such that continuity equation is satisfied if two components are u=x 2 +y 2 +z 2 , v=xy 2 – yz 2 + xy

a) -3xz-2xyz+z 2 /3+f

b) -3xz+2xyz+z 3 /3+f

c) -3xz-2xyz+z 3 /3+f

d) -3xz-2xyz+z 3 /3+f

Answer: d

Explanation: The continuity equation for incompressible is du/dx+dv/dy+dw/dz = 0.

Here du/dx=2x and v=2xy-z 2

On solving by integrating, we get w = -3xz-2xyz+z 3 /3+f,

4. A fluid flow field is given by

V=x 2 yi+y 2 z-k

Calculate it’s acceleration at the point 

a) 28i-3j+125k

b) 28i-3j-125k

c) 28i+3j+125k

d) None of the mentioned

Answer: d

Explanation: First we have to check whether it satisfies the continuity equation,

The continuity equation for incompressible is du/dx+dv/dy+dw/dz = 0.

The given equation doesn’t satisfy the continuity equation.

5. A fluid flow field is given by

V=y 2 xi+z 2 x-k

Calculate it’s acceleration at the point 

a) 36i-27j+100k

b) 36i-27j-100k

c) 28i+27j+100k

d) 36ne of the mentioned

Answer: d

Explanation: First we have to check whether it satisfies the continuity equation,

The continuity equation for incompressible is du/dx+dv/dy+dw/dz = 0.

The given equation doesn’t satisfy the continuity equation.

6. Convective acceleration cannot be found if the fluid flow equation is not satisfying

the continuity equation but local acceleration can be found.

a) True

b) False

Answer: b

Explanation: Convective acceleration and local acceleration cannot be found if the fluid flow equation is not satisfying the continuity equation.

7. Local acceleration has constant value for a steady flow.

a) True

b) False

Answer: b

Explanation: Local acceleration is zero for a steady flow.

8. Total acceleration has the same value as convective acceleration in case of unsteady flow.

a) True

b) False

Answer: b

Explanation: Total acceleration has the same value as convective acceleration in case of steady flow as local acceleration value becomes zero.

9. Which equation must be perfunctorily satisfied while dealing with fluid flow problems?

a) Newton’s second law

b) Newton’s third law

c) Law of conservation of momentum

d) Continuity equation

Answer: d

Explanation: Continuity equation must be perfunctorily satisfied while dealing with fluid flow problems.

10. Convective acceleration is defined as the rate of change of velocity due to change of velocity with respect to time.

a) True

b) False

Answer: b

Explanation: Convective acceleration is defined as the rate of change of velocity due to change of position of fluid particles.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Types of Motion and Vortex Flow”.

1. When fluid element moves from one position to another, what type of motion is it?

a) Linear Translation

b) Linear Deformation

c) Angular Deformation

d) Rotation

Answer: a

Explanation: As per the definition, bodily movement of fluid element is translation.

2. When fluid element moves from one position to another and it undergoes c hange in its dimensions, what type of motion is it?

a) Linear Translation

b) Linear Deformation

c) Angular Deformation

d) Rotation

Answer: b

Explanation: As per the definition, bodily movement of fluid element causing it to change its dimension is linear deformation.

3. If there is change in angle contained by two sides. the average of the angle is

a) Linear Translation

b) Linear Deformation

c) Angular Deformation

d) Rotation

Answer: c

Explanation: As per the definition, the sum average of two angles is magnitude of angular deformation.

4. What is the magnitude of vorticity?

a) Twice of angular rotation

b) Thrice of angular rotation

c) Two and half times of angular rotation

d) Same as angular rotation

Answer: a

Explanation: It is the mathematical relation between the two.

5. The flow of fluid along curvilinear or curved path is known as

a) Curvilinear Flow

b) Circular Flow

c) Sink Flow

d) Vortex Flow

Answer: d

Explanation: The flow of fluid along curvilinear or curved path is known as Vortex flow.

6. When external torque is absent the type of vortex flow is

a) Circular vortex flow

b) Independent vortex flow

c) Free vortex flow

d) None of the mentioned

Answer: c

Explanation: Free vortex flow is due to the absence of any external force.

7. Which of the following is not an example of forced vortex flow?

a) Liquid contained in cylinder rotated about its axis

b) Flow of liquid inside impeller of a centrifugal pump

c) Flow of a water through runner of a turbine

d) Flow of the liquid around a circular bend in a pipe

Answer: d

Explanation: Flow of the liquid around a circular bend in a pipe is an example of free vortex flow.

8. Which of the following is not an example of free vortex flow?

a) Flow of a water through runner of a turbine

b) Flow of liquid through a hole provided at the bottom

c) A whirlpool in a river

d) Flow of the liquid around a circular bend in a pipe

Answer: a

Explanation: Flow of a water through runner of a turbine is an example of forced vortex flow.

9. Equation of motion for vortex flow does not take into account centrifugal force?

a) True

b) False

Answer: b

Explanation: Equation of motion for vortex flow does take into account centrifugal force.

10. Equation of motion for vortex flow does take into account shear force

a) True

b) False

Answer: b

Explanation: Equation of motion for vortex flow does not take into account shear force.

This set of Fluid Mechanics online test focuses on “Important Cases of Potential Flow”.

1. The characteristic of Ideal fluid are

a) Incompressible

b) Inviscid

c) Fluid velocity is uniform

d) Shear stress has a constant, non zero value

Answer: c

Explanation: As ideal fluid is inviscid, shear stress is zero.

2. Which of the following is not a case of ideal fluid flow?

a) Forced vortex Flow

b) Uniform Flow

c) Sink Flow

d) Superimposed flow

Answer: a

Explanation: Forced vortex Flow does not satisfy the characteristic of ideal fluid flow.

3.What is a special characteristic of uniform flow parallel to X axis?

a) Velocity is constant

b) Acceleration is constant

c) X- component of velocity is constant

d) None of the mentioned

Answer: a

Explanation: Velocity is constant in uniform flow.

4. The source flow is flow coming from a point and moving out in a circular manner.

a) True

b) False

Answer: a

Explanation: The source flow is flow coming from a point and moving out in a radial manner.

5. The sink flow is flow in which fluid moves radially inwards towards a point where it disappears at a variable rate.

a) True

b) False

Answer: b

Explanation: The sink flow is flow in which fluid moves radially inwards towards a point where it disappears at a constant rate.

6. The pattern for streamlines and equipotential lines is different for source and sink flow.

a) True

b) False

Answer: b

Explanation: The pattern for streamlines and equipotential lines is different for source and sink flow.

7. In free vortex flow, the flow is linear in nature.

a) True

b) False

Answer: b

Explanation: In free vortex flow, the flow is circular in nature.

8. What is the nature of streamlines of free vortex flow?

a) Concentric

b) Non-concentric

c) Linear

d) None of the mentioned

Answer: a

Explanation: The nature of streamlines of free vortex flow is concentric.

9. For source flow, the radial velocity increases as we move radially outward.

a) True

b) False

Answer: b

Explanation: There is an inverse relation between velocity and radial distance for source flow.

10. When is air assumed to be incompressible?

a) At low speed

b) At high speed

c) Independent of its speed

d) None of the mentioned

Answer: a

Explanation: Air is assumed to be incompressible at low speed.

This set of Fluid Mechanics online quiz focuses on “Important Cases of Super imposed Flow”.

1. When a uniform flow is flowing through a doublet, resultant flow obtained is

a) Flow past a Rankine oval of equal axes

b) Flow past a circular cylinder

c) All of the mentioned

d) None of the mentioned

Answer: c

Explanation: They both mean the same thing. They are different ways of interpreting the same phenomenon.

2. How many stagnation points are present in a source and sink pair in a uniform flow

a) Two

b) Three

c) One

d) None

Answer: a

Explanation: There are two stagnation points are present in a source and sink pair in a uniform flow.

3. Which of the following is not a type of superimposed flow?

a) Source and sink pair in uniform flow.

b) Double flow

c) A source and sink pair in turbulent flow.

d) A plane source in uniform flow

Answer: c

Explanation: There is no such kind of superimposed flow.

4. In the equation for steam function due to source steam function is inversely proportional to magnitude at discharge

a) True

b) False

Answer: a

Explanation: Steam function is directly proportional to magnitude of discharge.

5. Streamlines of doublet flow are family of circles tangent to a common axis.

a) True

b) False

Answer: a

Explanation: This is special characteristic of doublet flow.

6. What is the characteristic of stagnation point

a) Velocity is zero

b) Acceleration is uniform

c) Velocity is zero

d) Acceleration is zero

Answer: a

Explanation: At stagnation point velocity is zero, as the fluid comes at rest. This characteristic at stagnation point.

7. Potential lines for the source-sink pair will be eccentric non intersecting circles with their centers on the axis.

a) True

b) False

Answer: b

Explanation: The potential line for the source sink pair will be eccentric non intersecting circles with their centers on the axis.

8. What is the term used for a case where source and sink approach each other such, distance between them reduces and product of distance and discharge magnitude remains constant.

a) A plain pair

b) A doublet source in uniform

c) Hagen Poiseuille flow

d) Coutte flow

Answer: b

Explanation: This is a special case of superimposed flow called double flow.

9. What type of flow is obtained by superimposing two definite flow types{

a) Ideal

b) Potential

c) Both

d) None of the mentioned

Answer: c

Explanation: Any linear combination of two different types of flows will result in a potential and ideal flow.

10. The nature of streamlines in a flow net obtained by the combination of source and sink is-

a) Linear

b) Curvilinear

c) Circular

d) Random

Answer: c

Explanation: The combination of the source and sink would result in a flow net where streamlines will be circular axes.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Introduction to Fluid Dynamics”.

1. Which of the following is NOT a type of force considered in the Navier-Stokes equation?

a) Gravity force

b) Pressure force

c) Surface tension force

d) Viscous force

Answer: c

Explanation: Gravity, Pressure force and viscous forces together constitute the derivation of the Navier-Stokes equation. Though surface tension force act on a fluid in motion, it is considered to be negligible for the Navier-Stokes equation.

2. Which of the following equations is a result of momentum conservation for inviscid steady flows?

a) Bernoulli’s equation

b) Navier-Stokes equation

c) First law of thermodynamics

d) Euler’s equation

Answer: d

Explanation: Bernoulli’s equation is an energy conservation equation which is obtained by integration of the Euler equation. Navier-Stokes equation is a force balance equation. The first law of thermodynamics is an energy conservation equation, too. Euler’s equation is a momentum equation. This equation is valid for inviscid steady flows.

3. The Bernoulli’s equation in fluid dynamics is valid for _________

a) Compressible flows

b) Transient flows

c) Continuous flows

d) Viscous flows

Answer: c

Explanation: To answer this equation, we need to know the assumptions used in Bernoulli’s equation. The Bernoulli’s theorem is only valid for ideal, steady, incompressible, continuous, inviscid and irrotational flows. So, out of the options, only continuous flows fit in the assumptions.

4. A water flows through a pipe at a velocity 2 m/s. The pressure gauge reading is 2 bar. The datum head is given to be 2 m. Find the piezometric head. (Assume all Bernoulli’s assumptions, Density of water = 1000 kg/m 3 , g = 9.8 m/s 2 ).

a) 22.4 m

b) 22.6 m

c) 20.4 m

d) 20.6 m

Answer: a

Explanation: Piezometric head is the addition of pressure head and the datum head. The pressure head is given by P/ρg = 20.4 m. The datum head is 2 m, which makes it a total of 22.4 m. The velocity given is extra information.

5. A student wishes to find the velocity of air flowing through a pipe. He has a pressure gauge which displays only the dynamic pressure. The pressure gauge reads 0.018 mm Hg. Assume density of air to be 1.225 kg/m 3 , find the velocity V of air (ρHg = 13600 kg/m 3 ).

a) 4 m/s

b) 2 m/s

c) 20 m/s

d) 40 m/s

Answer: b

Explanation:  = 2.4 bar. Dynamic pressure is given by ρV 2 /2. Equating 2.4 bar with dynamic pressure gives V = 2 m/s.

6. If compressibility force and surface tension force are neglected from the Newton’s second law of motion, which of the following equations result?

a) Navier-Stokes equation

b) Euler’s equation

c) Bernoulli’s equation

d) Reynolds equation

Answer: d

Explanation: The Newton’s second law of motion comprises of 6 forces, namely, gravity, viscosity, pressure, turbulence, surface tension and compressibility forces. Reynolds equation comprises of 4 forces. Surface tension force and compressibility forces are neglected for finding Reynolds equation.

7. What does a pitot tube measure? Upon which principle does a pitot tube work?

a) Pressure, Bernoulli’s principle

b) Velocity, Bernoulli’s principle

c) Pressure, Euler’s equation

d) Velocity, Euler’s equation

Answer: a

Explanation: Even though a pitot tube may be primarily used to find velocity of a fluid, the Pitot tube measures pressure and not velocity. The Pitot tube works upon the Bernoulli’s principle as it gives us pressure heads.

8. The below figure shows a pipe with a circular cross section of diameter 5 cm on the left end and a square cross section with diagonal 5 cm on the right end. Water enters the left end with a velocity 20 m/s and leaves the right end with a velocity V 2 . Find V 2 .

fluid-mechanics-questions-answers-introduction-fluid-dynamics-q8

a) V 2 cannot be found as the length of the pipe is not given

b) V 2 cannot be found as the intermediate cross sections are not given.

c) 31.41 m/s

d) 20 m/s

Answer: c

Explanation: Apply continuity equation A 1 V 1 = A 2 V 2 . We find that the velocity comes out to be 31.41 m/s. The question can be answered without calculations if the concept is known. V 2 neither depends upon the length of the pipe nor on the intermediate cross sections if losses are neglected.

9. In the equation, fluid-mechanics-questions-answers-introduction-fluid-dynamics-q9 the unit of E CANNOT be written as ______

a) m 2 /s 2

b) J/kg

c) Pa/m 3

d) kg.m/s 2

Answer: d

Explanation: From the last term, we can deduce that m 2 /s 2 can be the unit of E. From the first term, we get Pa/m 3 and J/kg is equivalent. Kg.m/s 2 is not of the same dimension. Hence, that is the correct choice.

10. The best place to place a pitot tube on an aircraft for velocity measurement is just behind the jet engine.

a) True

b) False

Answer: b

Explanation: Pitot tube is used for velocity measurement or airspeed measurement of an aircraft. Placing a pitot tube behind the jet engine will give us the speed of the gas rejected by the jet engine instead of the airspeed, hence, giving us erroneous readings. The best placement would be at a point where the speed of air is closest to the airspeed as seen by the aircraft.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Newton’s Second Law”.

1. A point in a fluid flow where the flow has come to rest is called __________

a) Pressure point

b) Initial point

c) Flow point

d) Stagnation point

Answer: d

Explanation: Stagnation point is a point at which a flow field of the local velocity of a fluid is equal to zero. At this point, the fluid is brought to rest by the object. When the velocity is zero, the static pressure is maximum.

2. When a fluid is subjected to resistance, it undergoes a volumetric change due to __________

a) Strain

b) Cohesion

c) Adhesion

d) Compressibility

Answer: d

Explanation: Compressibility is defined as a measure of relative change in volume of a fluid. In fluid mechanics, it is also called as isothermal compressibility due to increase in pressure and temperature.

3. What does Kinematic Viscosity depend upon?

a) Density

b) Pressure

c) Fluid level

d) Fluid Flow

Answer: a

Explanation: Kinematic viscosity is a quantity that represents dynamic viscosity of a fluid per unit density. Density is a major factor that determines the kinematic viscosity. As the temperature increases, density decreases thereby causing changes in the density of the fluid.

4. What is the formula to find the kinematic viscosity of a fluid?

a) Dynamic Viscosity * Temperature

b) Dynamic Viscosity / Density

c) 1/ dynamic viscosity

d) Density / Dynamic Viscosity

Answer: b

Explanation: Density is a major factor that determines the kinematic viscosity. As the temperature increases, density decreases thereby causing changes in the density of the fluid. Thus, kinematic viscosity and density are inversely proportional.

5. A one dimensional flow is also called as __________

a) A steady flow

b) A flow which involves zero transverse component

c) Uniform Flow

d) Zig-Zag flow

Answer: b

Explanation: One dimensional flow is a flow in which variations of velocity and pressure occur along one space coordinate only. A good example of one dimensional flow is a flow through pipe. During a flow through a pipe, the functions of velocity and pressure occur along the length of the pipe.

6. What is the resultant upward pressure of a fluid on an immersed body called?

a) Buoyancy

b) Metacentre

c) Upthrust

d) Reaction pressure

Answer: a

Explanation: Buoyancy has been explained by Archimedes Principle. The principle states that the force exerted is directly proportional to the pressure difference. This equivalent weight of the body immersed is equal to that of the fluid displaced.

7. If a mass of 1000kg of liquid occupies a volume of one cubic meter, then 1 represents which among the following?

a) Specific Density

b) Specific Weight

c) Specific Gravity

d) Specific Mass

Answer: c

Explanation: Specific Gravity is defined as the ratio of mass or density of a substance to that of the mass or density of a reference substance. But, provided that it has the same volume. It must also have a specified temperature and pressure.

8. At what temperature is the density of water the maximum?

a) 100 o C

b) 0 o C

c) 5 o C

d) 0 K

Answer: c

Explanation: Heating a substance leads to faster movement of molecules due to which density decreases. Whereas, cooling a substance leads to a slower movement of molecules and occupies a smaller volume. Thus, increasing its density.

9. When is a fluid said to be ideal?

a) Non viscous and Incompressible

b) Viscous and compressible

c) Viscous and Incompressible

d) Incompressible

Answer: a

Explanation: Ideal fluids are fluids that have a zero viscosity. This result in a flow called as inviscid flow. Inviscid flow is non viscous and incompressible since there is no existence of shear force due to zero viscosity.

10. If a flow is having the same parameters at any given point, then it is said to be_________

a) Uniform flow

b) Quasi static flow

c) Laminar flow

d) Static flow

Answer: a

Explanation: A flow that takes place at a constant speed without the change in cross section is called a uniform flow. Its parameters remain a constant at any given point.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “First Law of Thermodynamics”.

1. First law of thermodynamics deals with _______

a) Conservation of mass

b) Conservation of momentum

c) Conservation of energy

d) Conservation of pressure

Answer: c

Explanation: First law corresponds to the law of conservation of energy. It states that energy can neither be created nor destroyed, but can be transformed from one form to the other. It follows the principle of heat transfer and energy transfer.

2. Equation of the first law of thermodynamics is ________

a) Internal Energy= Heat added into work done

b) Internal Energy= Heat rejected into work done

c) Internal Energy= Heat added divided by work done

d) Internal Energy=Heat added plus work done

Answer: d

Explanation: It is a thermodynamic expression which gives a relationship between internal energy, heat and work done. Work done on the system is positive, and work done by the system is negative. The standard unit of all these quantities is Joule.

3. During a fluid flow, the temperature is developed due to________

a) Increase in density

b) Change in pressure

c) Translational Kinetic Energy

d) Fluid level

Answer: c

Explanation: When there is a high rate of fluid flow, the molecules tend to collide with each other. At this state, the average translational kinetic energy of the particles increases. The temperature developed due to this is called as Kinetic temperature.

4. The equation for the average kinetic energy is_________

a) 0.5 KT

b) 1.5 KT

c) 2.5 KT

d) 3.5 KT

Answer: b

Explanation: The equation for kinetic energy is 0.5mv 2 , where m= mass and v= velocity. This equation corresponds to 1.5 KT, where K=Boltzmann’s constant and R= Gas constant.

5. An increase in enthalpy leads to an increase in __________

a) Increase in pressure

b) Increase in volume

c) Increase in internal energy

d) Increase in mass

Answer: c

Explanation: When the temperature increases, the amount of molecular interactions also increases. Using the equation from the first law of thermodynamics, internal energy also increases with the increase in temperature. Thus, increase in enthalpy leads to an increase in internal energy.

6. Entropy occurs due to _______

a) Change in macroscopic variables

b) Volumetric changes only

c) Mass changes only

d) Temperature only

Answer: a

Explanation: Entropy is related to a number of microscopic configurations. It can have some of the most specified macroscopic variables. These macroscopic variables undergo changes, which lead to a disorder or randomness.

7. What is the equation of entropy?

a) Ratio of reversible transfer of heat to absolute temperature

b) Ratio of absolute temperature to reversible heat transfer

c) Ratio of adiabatic heat to macroscopic variables

d) Ratio of macroscopic variables to adiabatic heat

Answer: a

Explanation: This equation was defined by Rudolf Clausius, who defined entropy as a ratio of reversible heat transfer to that of its absolute temperature. This definition is also called the macroscopic definition of entropy.

8. SI unit of enthalpy is_______

a) Joule/kgK

b) Joule/K

c) Joule/kg

d) K/kg

Answer: c

Explanation: Enthalpy is defined as a measurement of energy in a thermodynamic system. It is equal to the internal energy plus the product of volume and pressure. Thus, giving a unit of Joule/kg.

9. Which among this is not an exothermic reaction?

a) Combustion reaction

b) Neutralization reaction

c) Thermite reaction

d) Evaporating liquid water

Answer: d

Explanation: Exothermic reaction is a reaction that releases energy by either light or heat. It is the opposite of endothermic reactions. In this case, evaporating liquid water is an endothermic reaction. Endothermic reaction is a reaction in which the system absorbs heat from its surroundings.

10. What reaction takes place during photosynthesis?

a) Exothermic reaction

b) Endothermic reaction

c) Redox reaction

d) Combustion reaction

Answer: b

Explanation: Photosynthesis takes place by absorbing heat and energy from the surroundings. Since, endothermic reaction is a reaction in which the system absorbs heat from its surroundings, the reaction that takes place during photosynthesis is an endothermic reaction.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Navier-Stokes Equations of Motion”.

1. Navier- Stokes equation describes the motion of __________

a) Solid substance

b) Non-viscous fluid

c) Viscous fluid

d) Gas

Answer: c

Explanation: The equation described by Navier- Stokes is for a viscous fluid. The balanced equation arises from Newton’s Second Law of fluid motion. It assumes that the stress in the fluid is equal to the sum of a diffusing viscous term and a pressure term.

2. Froude number depends upon_________

a) Flow velocity, external field and characteristic length

b) Flow velocity and mass

c) Mass flow rate and volume

d) Characteristic length and volume

Answer: a

Explanation: The Froude number is a dimensionless number. It is defined as the ratio of flow inertia to the external field. The Froude number is based on the speed-length ratio.

3. Continuum mechanics is a branch of mechanics that deals with________

a) Fluid particles

b) Discrete particles

c) Kinematics and mechanical behaviour

d) Hydrostatic Pressure

Answer: c

Explanation: Continuum mechanics is a branch that deals with the analysis of kinematics and mechanical behaviour of materials. It can be modelled as a continuous mass rather than as discrete particles.

4. Which among the following cannot be used as an alternative term for a “solenoidal vector field”?

a) Incompressible vector field

b) Divergence- free vector field

c) Transverse vector field

d) Continuous random field

Answer: d

Explanation: A random field comes under a stochastic process. It can take up values that are multidimensional vectors or points on some manifold. A random field is a list of random numbers whose indices are identified with a discrete set of points in space.

5. The Navier- Stokes equation can be used in which of the following applications?

a) Automobiles

b) Ocean Currents

c) Airplanes

d) Thermometer

Answer: b

Explanation: An ocean current is a continuous direct movement of seawater. Ocean currents are forces generated by acting upon the mean flow. Therefore, ocean currents satisfy Navier-Stokes equation as they have a primary horizontal water movement.

6. Which among the following is not an example of magneto fluids?

a) Plasma

b) Liquid metals

c) Salt water

d) Alcohol

Answer: d

Explanation: Alcohol is an organic compound on which a hydroxyl functional group is bounded to a saturated carbon atom. Alcohols work as an antifreeze solution at cool temperatures. Thus, it is not a magneto fluid.

7. What is the velocity profile for Poiseuille flow?

a) Zero

b) Constant

c) Linear

d) Quadratic

Answer: d

Explanation: The velocity profile for Poiseuille flow is zero at either side of the channel and non-zero in the middle. Therefore, Quadratic equation is the only possible option here.

8. What are the Newtonian constitutive assumptions regarding relationship between stress tensor and velocity gradients?

a) Linear and isotropic

b) Constant

c) Linear

d) Non-Uniform

Answer: a

Explanation: Newtonian fluid is a fluid in which the viscous stresses arise due to its flow. The flow experiences a strain rate at every point. The strain rate is related to the constant viscosity tensor that does not depend upon the stress and velocity of the flow. Thus, the relationship is linear and isotropic.

9. What is the incompressibility condition in Navier-Stokes equation?

a) ∇.u=0

b) ∇.u>0

c) ∇.u<0

d) ∇.u=1

Answer: a

Explanation: This comes from the relation between the divergence of the flow. It also relates the Jacobian transformation with Lagrangian and Eulerian coordinates. Thus, ∇.u=0.

10. The velocity profile of the Couette flow is _______

a) Quadratic

b) Constant

c) Linear

d) Zero

Answer: c

Explanation: Couette flow is a flow of viscous fluid in the space between two surfaces. One surface moves tangentially with respect to the other. The configuration often takes the form of the two parallel plates or the gaps in between two cylinders.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Impulse Momentum Equation”.

1. When a cricket bat hits a cricket ball, impulse is applied on the_________

a) Bat

b) Ball

c) Bat and ball

d) No impulse is applied

Answer: b

Explanation: Time passes as force is applied on an object. The bat applies the force on the ball for a short period of time. By this way, we can say in accordance to the Newton’s third law forces come in pairs. So, the ball also applies a force on the bat, therefore it has an impulse applied to it.

2. Momentum is a ______ quantity

a) Scalar

b) Vector

c) Infinite

d) Zero

Answer: b

Explanation: Momentum is a vector quantity as it has both size and direction. Size of the momentum is equal to the mass of the object into the size of the objects velocity. The direction of objects velocity is the same as the direction of the momentum.

3. The equation for impulse is_______

a) F∆t=m∆v

b) F∆t=mu

c) F∆t=mT

d) F∆t=mRT

Answer: a

Explanation: Impulse is equal to the net force times the length of time over which the force is applied on the body of the fluid. On the right hand side, we have the change in momentum. Thus, option ‘a’ is the most suitable one.

4. What is the SI unit of impulse?

a) N/m

b) N/m 2

c) N.s

d) Kg.m

Answer: c

Explanation: The SI unit of impulse is Newton second. It is given by the linear momentum due to the vector change. This produces an impulse in the same direction with respect to a given time.

5. What is the SI unit of momentum?

a) kgm/s

b) kgm/s 2

c) kgm/s 3

d) kg.m 2

Answer: a

Explanation: The SI unit of momentum is given by the product of the units of mass and velocity. In SI units,  and . As we know that momentum is mass times velocity. The unit turns out to be kgm/s.

6. Change in momentum of an object is equal to the_______

a) Internal Energy

b) Entropy

c) Impulse

d) Enthalpy

Answer: c

Explanation: The mass is distributed over two velocities. According to the Newton’s second law, the change in momentum is equal to the impulse so produced. Since, momentum is a quantity that describes an object’s resistance to stopping. It is equated with its impulse.

7. What is the unit of specific impulse?

a) m/s

b) m 2 /s

c) m 3 /s

d) m/s 2

Answer: a

Explanation: Specific impulse is equal to the exhaust velocity of the fluid. Since, the unit of exhaust velocity is m/s, the unit of specific impulse is also the same. It is used to measure the efficacy of rocket propellants.

8. What is the formula to find specific impulse?

a) J sp =m/v

b) J sp = J/m

c) J sp =T/m

d) J sp =J/q

Answer: b

Explanation: Specific impulse is defined as impulse per weight. It can also be defined as thrust per weight of a flow rate. It is equal to the exhaust velocity divided by acceleration due to gravity. 

9. Angular momentum is a _______ quantity

a) Scalar

b) Vector

c) Infinite

d) Finite

Answer: b

Explanation: Angular momentum is a vector quantity as it has both size and direction. Size of the momentum is equal to the mass of the object into the size of the object’s velocity. The direction of objects velocity is the same as the direction of the momentum.

10. Angular momentum is proportional to __________

a) Inertia and angular speed

b) Mass and angular speed

c) Angular speed and volume

d) Rate of change of angular speed

Answer: a

Explanation: Moment of inertia is not only dependent on the amount of matter. It also depends upon the position of axis of rotation and the shape of the matter. . Thus, inertia and angular speed play an important role in determining the angular momentum.

This set of Fluid Mechanics Question Bank focuses on “Bernoulli’s Equation for Real Fluids & Applications of Bernoulli’s Equation”.

1. Which is the cheapest device for measuring flow / discharge rate.

a) Venturimeter

b) Pitot tube

c) Orificemeter

d) None of the mentioned

Answer: c

Explanation: Orificemeter is the cheapest available device for measuring flow/discharge rate.

2. The principle of Orificemeter is same as that of Venturimeter.

a) True

b) False

Answer: a

Explanation: The working principle for both Orificemeter and Venturimeter is same.

3. What is the relationship between Orificemeter diameter and pipe diameter

a) Orificemeter diameter is 0.5 times the pipe diameter

b) Orificemeter diameter is one third times the pipe diameter

c) Orificemeter diameter is one fourth times the pipe diameter

d) Orificemeter diameter is equal to the pipe diameter

Answer: c

Explanation: None.

4. The Orificemeter readings are more accurate than Venturimeter.

a) True

b) False

Answer: b

Explanation: The Venturimeter readings are more accurate than Orificemeter.

5. The Orificemeter readings are more accurate than Pitot tube readings.

a) True

b) False

Answer: b

Explanation: The Pitot tube readings are more accurate than Orificemeter.

6. The Orificemeter has a smooth edge hole.

a) True

b) False

Answer: b

Explanation: The Orificemeter has a rough edge hole.

7. A nanometre is connected to a section which is at a distance of about 4 to 6 times the pipe diameter upstream from orifice plate.

a) True

b) False

Answer: b

Explanation: A manometre is connected to a section which is at a distance of about 1.5 to 2.0 times the pipe diameter upstream from orifice plate.

8. Venturimeter is based on integral form of Euler’s equation.

a) True

b) False

Answer: a

Explanation: Venturimeter is based on Bernoulli’s equation.

9. Orifice Meter can only be used for measuring rate of flow in open pipe like structure.

a) True

b) False

Answer: a

Explanation: Orificemetre can only be used for measuring rate of flow in an enclosed pipe like structure.

10. Orifice meter consists of a flat rectangular plate.

a) True

b) False

Answer: b

Explanation: Orifice meter consists of a flat circular plate.

This set of Fluid Mechanics Questions and Answers for Entrance exams focuses on “Classification of Orifice & Hydraulic Coefficients”.

1. When is orifice called ‘large orifice’?

a) If the head of liquid is less than 5 times the depth of orifice

b) If the head of liquid is less than 2.5 times the depth of orifice

c) If the head of liquid is less Hence, 4 times the depth of orifice

d) If the head of liquid is less than 1.5 times the depth of orifice

Answer: a

Explanation: It is the correct parametric definition for ‘large orifice’.

2. In case of any orifice, velocity always remains constant and hence discharge can be calculated.

a) True

b) False

Answer: b

Explanation: In case of large orifice, velocity always remains variable and hence discharge cannot be calculated.

3. Find the discharge through a rectangular orifice 2.2 m wide and 1.3 m deep fitted to a easier tank. The water level in a team is 2.5 m above the top edge of orifice.

a) 13.9 m 3 /s

b) 11.5 m 3 /s

c) 16.9 m 3 /s

d) 8.7 m 3 /s

Answer: a

Explanation: Q = 2/3 Cd *b*√2g* (H2 1.5 – H1 1.5 )

Here,

H1 = 3.8

H2 = 2.5

b = 2.2

Hence, Q = 13.9 m3/s.

4. Find the discharge through a rectangular orifice 3.2 m wide and 1.7 m deep fitted to a easier tank. The water level in a team is 3.3 m above the top edge of orifice. Take Cd = 0.6

a) 29.4 m 3 /s

b) 58.5 m 3 /s

c) 67.9 m 3 /s

d) 78.7 m 3 /s

Answer: a

Explanation: Q = 2/3 Cd *b*√2g* (H2 1.5 – H1 1.5 )

Here,

H1 = 5

H2 = 3.3

b = 3.2

Hence, Q = 29.4 m3/s.

5. Find the discharge through totally drowned orifice of width 2.3 m if the difference of water levels on both side of the orifice be 40 cm. The height of water from to and bottom of the orifice are 2.6 m and 2.75 m respectively.

a) .56 m 3 /s

b) .64 m 3 /s

c) .75 m 3 /s

d) .55 m 3 /s

Answer: a

Explanation: Q = Cd * b *  √2gH

Here, b = 2.3

H2 = 2.75

H1 = 2.6

H = 40

Q = .56 m 3 /s.

6. Find the discharge through totally drowned orifice of width 3.3 m if the difference of water levels on both side of the orifice be 50 cm. The height of water from to and bottom of the orifice are 2.25 m and 2.67 m respectively.

a) 2.8 m 3 /s

b) 2.7 m 3 /s

c) 2.6 m 3 /s

d) 2.5 m 3 /s

Answer: a

Explanation: Q = Cd * b *  √2gH

Here, b = 3.3

H2 = 2.67

H1 = 2.25

H = 50

Q = 2.6 m 3 /s.

7. A rectangular orifice of 2 m width and 1.2 m deep is fitted in one side of large tank. The easier level on one side of the orifice is 3m above the top edge of the orifice while on the other side of the orifice the water level is 0.5 m below it’s top edge. Calculate discharge if Cd = .64

a) 4.95 m 3 /s

b) 5.67 m 3 /s

c) 3.56 m 3 /s

d) 6.75 m 3 /s

Answer: a

Explanation: Explanation: Q = Cd * b *  √2gH

Here, b = 2

H2 = 4.2

H = 3.5

Q = 4.94 m 3 /s.

8. The time taken to empty the tank is independent of Cd but depends only on the height and acceleration due to gravity.

a) True

b) False

Answer: b

Explanation: The time taken to empty the tank is dependent on Cd as well as depends only on the height and acceleration due to gravity.

9. The discharge rate is independent of the height difference and dependent only on the height.

a) True

b) False

Answer: b

Explanation: The discharge rate is dependent of the height difference and dependent only on the height.

10. In case of submerged orifice the discharge is substantially dependent on temperature of fluid

a) True

b) False

Answer: b

Explanation: Discharge is dependent on temperature but minimally.

This set of Fluid Mechanics Questions and Answers for Entrance exams focuses on “Classification of Orifice & Hydraulic Coefficients”.

1. When is orifice called ‘large orifice’?

a) If the head of liquid is less than 5 times the depth of orifice

b) If the head of liquid is less than 2.5 times the depth of orifice

c) If the head of liquid is less Hence, 4 times the depth of orifice

d) If the head of liquid is less than 1.5 times the depth of orifice

Answer: a

Explanation: It is the correct parametric definition for ‘large orifice’.

2. In case of any orifice, velocity always remains constant and hence discharge can be calculated.

a) True

b) False

Answer: b

Explanation: In case of large orifice, velocity always remains variable and hence discharge cannot be calculated.

3. Find the discharge through a rectangular orifice 2.2 m wide and 1.3 m deep fitted to a easier tank. The water level in a team is 2.5 m above the top edge of orifice.

a) 13.9 m 3 /s

b) 11.5 m 3 /s

c) 16.9 m 3 /s

d) 8.7 m 3 /s

Answer: a

Explanation: Q = 2/3 Cd *b*√2g* (H2 1.5 – H1 1.5 )

Here,

H1 = 3.8

H2 = 2.5

b = 2.2

Hence, Q = 13.9 m3/s.

4. Find the discharge through a rectangular orifice 3.2 m wide and 1.7 m deep fitted to a easier tank. The water level in a team is 3.3 m above the top edge of orifice. Take Cd = 0.6

a) 29.4 m 3 /s

b) 58.5 m 3 /s

c) 67.9 m 3 /s

d) 78.7 m 3 /s

Answer: a

Explanation: Q = 2/3 Cd *b*√2g* (H2 1.5 – H1 1.5 )

Here,

H1 = 5

H2 = 3.3

b = 3.2

Hence, Q = 29.4 m3/s.

5. Find the discharge through totally drowned orifice of width 2.3 m if the difference of water levels on both side of the orifice be 40 cm. The height of water from to and bottom of the orifice are 2.6 m and 2.75 m respectively.

a) .56 m 3 /s

b) .64 m 3 /s

c) .75 m 3 /s

d) .55 m 3 /s

Answer: a

Explanation: Q = Cd * b *  √2gH

Here, b = 2.3

H2 = 2.75

H1 = 2.6

H = 40

Q = .56 m 3 /s.

6. Find the discharge through totally drowned orifice of width 3.3 m if the difference of water levels on both side of the orifice be 50 cm. The height of water from to and bottom of the orifice are 2.25 m and 2.67 m respectively.

a) 2.8 m 3 /s

b) 2.7 m 3 /s

c) 2.6 m 3 /s

d) 2.5 m 3 /s

Answer: a

Explanation: Q = Cd * b *  √2gH

Here, b = 3.3

H2 = 2.67

H1 = 2.25

H = 50

Q = 2.6 m 3 /s.

7. A rectangular orifice of 2 m width and 1.2 m deep is fitted in one side of large tank. The easier level on one side of the orifice is 3m above the top edge of the orifice while on the other side of the orifice the water level is 0.5 m below it’s top edge. Calculate discharge if Cd = .64

a) 4.95 m 3 /s

b) 5.67 m 3 /s

c) 3.56 m 3 /s

d) 6.75 m 3 /s

Answer: a

Explanation: Explanation: Q = Cd * b *  √2gH

Here, b = 2

H2 = 4.2

H = 3.5

Q = 4.94 m 3 /s.

8. The time taken to empty the tank is independent of Cd but depends only on the height and acceleration due to gravity.

a) True

b) False

Answer: b

Explanation: The time taken to empty the tank is dependent on Cd as well as depends only on the height and acceleration due to gravity.

9. The discharge rate is independent of the height difference and dependent only on the height.

a) True

b) False

Answer: b

Explanation: The discharge rate is dependent of the height difference and dependent only on the height.

10. In case of submerged orifice the discharge is substantially dependent on temperature of fluid

a) True

b) False

Answer: b

Explanation: Discharge is dependent on temperature but minimally.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Flow through Large Orifice”.

1. When is orifice called ‘large orifice’?

a) If the head of liquid is less than 5 times the depth of orifice

b) If the head of liquid is less than 2.5 times the depth of orifice

c) If the head of liquid is less Hence, 4 times the depth of orifice

d) If the head of liquid is less than 1.5 times the depth of orifice

Answer: a

Explanation: It is the correct parametric definition for ‘large orifice’.

2. In case of any orifice, velocity always remains constant and hence discharge can be calculated.

a) True

b) False

Answer: b

Explanation: In case of large orifice, velocity always remains variable and hence discharge cannot be calculated.

3. Find the discharge through a rectangular orifice 2.2 m wide and 1.3 m deep fitted to a easier tank. The water level in a team is 2.5 m above the top edge of orifice.

a) 13.9 m 3 /s

b) 11.5 m 3 /s

c) 16.9 m 3 /s

d) 8.7 m 3 /s

Answer: a

Explanation: Q = 2/3 Cd *b*√2g* (H2 1.5 – H1 1.5 )

Here,

H1 = 3.8

H2 = 2.5

b = 2.2

Hence, Q = 13.9 m 3 /s.

4. Find the discharge through a rectangular orifice 3.2 m wide and 1.7 m deep fitted to a easier tank. The water level in a team is 3.3 m above the top edge of orifice. Take Cd = 0.6

a) 29.4 m 3 /s

b) 58.5 m 3 /s

c) 67.9 m 3 /s

d) 78.7 m 3 /s

Answer: a

Explanation: Q = 2/3 Cd *b*√2g* (H2 1.5 – H1 1.5 )

Here,

H1 = 5

H2 = 3.3

b = 3.2

Hence, Q = 29.4 m 3 /s.

5. Find the discharge through totally drowned orifice of width 2.3 m if the difference of water levels on both side of the orifice be 40 cm. The height of water from to and bottom of the orifice are 2.6 m and 2.75 m respectively.

a) .56 m 3 /s

b) .64 m 3 /s

c) .75 m 3 /s

d) .55 m 3 /s

Answer: a

Explanation: Q = Cd * b *  √2gH

Here, b = 2.3

H2 = 2.75

H1 = 2.6

H = 40

Q = .56 m 3 /s.

6. Find the discharge through totally drowned orifice of width 3.3 m if the difference of water levels on both side of the orifice be 50 cm. The height of water from to and bottom of the orifice are 2.25 m and 2.67 m respectively.

a) 2.8 m 3 /s

b) 2.7 m 3 /s

c) 2.6 m 3 /s

d) 2.5 m 3 /s

Answer: a

Explanation: Q = Cd * b *  √2gH

Here, b = 3.3

H2 = 2.67

H1 = 2.25

H = 50

Q = 2.6 m 3 /s.

7. A rectangular orifice of 2 m width and 1.2 m deep is fitted in one side of large tank. The easier level on one side of the orifice is 3m above the top edge of the orifice while on the other side of the orifice the water level is 0.5 m below it’s top edge. Calculate discharge if Cd = .64

a) 4.95 m 3 /s

b) 5.67 m 3 /s

c) 3.56 m 3 /s

d) 6.75 m 3 /s

Answer: a

Explanation: Explanation: Q = Cd * b *  √2gH

Here, b = 2

H2 = 4.2

H = 3.5

Q = 4.94 m 3 /s.

8. The time taken to empty the tank is independent of Cd but depends only on the height and acceleration due to gravity.

a) True

b) False

Answer: b

Explanation: The time taken to empty the tank is dependent on Cd as well as depends only on the height and acceleration due to gravity.

9. The discharge rate is independent of the height difference and dependent only on the height.

a) True

b) False

Answer: b

Explanation: The discharge rate is dependent of the height difference and dependent only on the height.

10. In case of submerged orifice the discharge is substantially dependent on temperature of fluid

a) True

b) False

Answer: b

Explanation: Discharge is dependent on temperature but minimally.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Classification of Notches and Weirs”.

1. A notch is a device used to measure the turbulence of the flowing liquid directly.

a) True

b) False

Answer: b

Explanation: A notch is a device used to measure the flow rate of the flowing liquid, directly.

2. The weir is an attachable structure made up of thermoplastic.

a) True

b) False

Answer: b

Explanation: The weir is a permanent masonry structure made up of concrete.

3. The notch is bigger in size than wier.

a) True

b) False

Answer: b

Explanation: The weir is bigger in size than notch.

4. The MoM  of notch is,

a) Thermoplastic

b) Metals

c) Fibre

d) Wood

Answer: b

Explanation: The MoM  of notch is Metals.

5. Which of the following is not a way of classifying notches or weirs?

a) Based on the shape of opening

b) Based on the effect of the sides on the nappe

c) Based on the shape of the crest

d) Based on the effect of the sides on the crest

Answer: d

Explanation: There is no such way of classification.

6. The nature of discharge is also a way of classifying notches.

a) True

b) False

Answer: b

Explanation: The nature of discharge is also a way of classifying notches.

7. Which of the following is not a way of classifying based on the shape of opening?

a) Rectangular notch

b) Circular notch

c) Trapezoidal notch

d) Stepped notch

Answer: b

Explanation: Circular notch is not a way of classifying based on the shape of opening.

8. Trapezoidal weir has another popular name. What is it?

a) Cipolletti weir

b) Hagen Poiseuille’s weir

c) Reynold’s weir

d) Euler’s weir

Answer: a

Explanation: Trapezoidal weir is also called Cipolletti weir.

9. What is not the way of classifying weir based on their shape of crest?

a) Sharp crested weir

b) Broad crested weir

c) Narrow crested weir

d) Trapezoidal crested weir

Answer: d

Explanation: Trapezoidal crested weir is not the way of classifying weir based on their shape of crest.

10. What is not the way of classifying weir based on the emerging nappe?

a) Weir with end contraction

b) Weir without end contraction

c) Weir contraction at the beginning

d) Weir with absence of end contraction

Answer: c

Explanation: This is not the way of classifying weir based on the emerging nappe.

This set of Fluid Mechanics Questions and Answers for Campus interviews focuses on “Discharge over a Rectangular Notch, Triangular Notch, Trapezoidal Notch and Stepped Notch”.

1. Find the discharge of water flowing over a rectangular notch of 1.5 m length when the constant head over the notch is 275 mm. Take Cd = .60

a) 400 lit/s

b) 465 lit/s

c) 385 lit/s

d) 575 lit/s

Answer: c

Explanation: Q = 2/3 * L * √2g * H 1.5

= .67 * 1.5 * √19.62 * .275 1.5

= .385 m 3 /min.

2. The head of water over a rectangular notch is 900 mm. The discharge is 300 litres/s. Find the length of the notch, when CD =.62

a) .192 m

b) .250 m

c) .205 m

d) .175 m

Answer: a

Explanation: L = 1.5 * Q / (Cd * √2g * H 1.5 )

= 1.5 * .3 / (.62 * √19.62 * .9 1.5 )

= .192 m.

3. Find the discharge of water flowing over a rectangular notch of 1.3 m length when the constant head over the notch is 255 mm. Take Cd = .62

a) 400 lit/s

b) 465 lit/s

c) 385 lit/s

d) 575 lit/s

Answer: a

Explanation: Q = 2/3 * L * √2g * H 1.5

= .67 * 1.3 * √19.62 * .255 1.5

= .385 m 3 /min.

4. The head of water over a rectangular notch is 700 mm. The discharge is 200 litres/s. Find the length of the notch, when CD =.63

a) .125 m

b) .265 m

c) .250 m

d) .200 m

Answer: a

Explanation: L = 1.5 * Q / (Cd * √2g * H 1.5 )

= 1.5 * .2 / (.62 * √19.62 * .7 1.5 )

= .125 m.

5. Find the discharge over triangular notch of angle 50° when the head over the V notch

a) .93 m 3 /min

b) 1.45 m 3 /min

c) .88 m 3 /min

d) .90 m 3 /min

Answer:a

Explanation: Q = 8/15 * √2g * H 1.5 * tan

Here, x is the angle.

= 8/15 * √19.62 * .22 1.5 * tan

= .93 m 3 /min.

6. The expression for discharge for a right angled notch is more complex than rectangular notch.

a) True

b) False

Answer: b

Explanation: The expression for discharge for a right angled notch is easier than rectangular notch.

7. The results of which are more accurate; rectangular notch or triangular weir.

a) Rectangular notch

b) Triangular weir

c) Both are equally accurate

d) Rectangular weir

Answer: b

Explanation: The results of triangular notch are more accurate for low discharge.

8. What is main reading required in calculation for rectangular notch or weir.

a) H

b) x, x is angle

c) L

d) None of the mentioned

Answer: a

Explanation: H i.e height is main reading required in calculation for rectangular notch or weir.

9. We need to obligatorily have ventilation in triangular notch.

a) True

b) False

Answer: b

Explanation: We need not obligatorily have ventilation in triangular notch.

10. Rectangular notch may or may not have ventilation.

a) True

b) False

Answer: b

Explanation: Rectangular notch must have ventilation.

This set of Fluid Mechanics Questions and Answers for Aptitude test focuses on “Time Required to Empty a Reservoir Or a Tank with a Rectangular, Triangular & Cipolletti Weir or Notch”.

1. What is the reduction in crest length due to each end contraction?

a) 0.1H

b) 0.2H

c) 0.15H

d) 0.25H

Answer: a

Explanation: Francis through his experiment had derived this empirical relation.

2. In Francis formula, the effective length is –

a) L-0.2H

b) L-0.4H

c) L-0.3H

d) L-0.1H

Answer: a

Explanation: In Francis formula, the effective length is L-0.2H.

3. In Francis empirical expression for discharge, the relation between head of water and discharge is

a) Q is directly proportional to H

b) Q is directly proportional to H 1.5

c) Q is directly proportional to H 2.5

d) Q is directly proportional to H 0.5

Answer: b

Explanation: In Francis empirical expression for discharge, the relation between head of water and discharge is Q is directly proportional to H 1.5 .

4. In Bazin’s formula, the discharge is inversely proportional to the length of weir.

a) True

b) False

Answer: b

Explanation: In Bazin’s formula, the discharge is directly proportional to the length of weir.

5. The head of water over a rectangular weir is 38 cm. The length of the crest of the weir end contraction suppressed is 1.3 m. Find the discharge using the Francis formula.

a) 0.56 m 3 /s

b) 0.75 m 3 /s

c) 0.85 m 3 /s

d) 0.69 m 3 /s

Answer: a

Explanation: Q = 1.84*L*H 1.5 = 0.56 m 3 /s.

6. The head of water over a rectangular weir is 28 cm. The length of the crest of the weir end contraction suppressed is 1.27 m. Find the discharge using the Francis formula.

a) 0.346 m 3 /s

b) 0.556 m 3 /s

c) 0.788 m 3 /s

d) 0.225 m 3 /s

Answer: a

Explanation: Q = m * L *  0.5 * H 1.5

m = ⅔ * Cd

= 0.405 + 0.003/H

= 0.405 + 0.003/0.28

Q = 0.346 m 3 /s.

7. The head of water over a rectangular weir is 26 cm. The length of the crest of the weir end contraction suppressed is 1.25 m. Find the discharge using the Francis formula.

a) 0.304 m 3 /s

b) 0.502 m 3 /s

c) 0.350 m 3 /s

d) 0.625 m 3 /s

Answer: a

Explanation: Q = 1.84*L*H 1.5

= 0.304 m 3 /s.

8. The head of water over a rectangular weir is 28 cm. The length of the crest of the weir end contraction suppressed is 1.27 m. Find the discharge using the Francis formula.

a) 0.346 m 3 /s

b) 0.556 m 3 /s

c) 0.788 m 3 /s

d) 0.225 m 3 /s

Answer: a

Explanation: Q = m * L *  0.5 * H 1.5

m = ⅔ * Cd

= 0.405 + 0.003/H

= 0.405 + 0.003/0.28

Q = 0.346 m 3 /s.

9. Find the discharge over a cipolletti weir of length 1.5 m when the head over the weir is 0.85 m. Take Cd = 0.61.

a) 2.12 m 3 /s

b) 1.25 m 3 /s

c) 2.5 m 3 /s

d) 1.5 m 3 /s

Answer: a

Explanation: Q = ⅔ * Cd * L *  0.5 * H 1.5

= 2.12 m 3 /s.

10. Find the discharge over a cipolletti weir of length 1.3 m when the head over the weir is 0.65 m. Take Cd = 0.60.

a) 2.12 m 3 /s

b) 1.21 m 3 /s

c) 2.5 m 3 /s

d) 1.5 m 3 /s

Answer: b

Explanation: Q = ⅔ * Cd * L *  0.5 * H 1.5

= 1.21 m 3 /s.

This set of Fluid Mechanics Assessment Questions and Answers focuses on “Discharge Over Broad-Crested Weir, Narrow Crested Weir, Ogee Weir, Submerged or Drowned Weir”.

1. In discharge of water over narrow crested weir, head of water is directly proportional to Discharge Coefficient.

a) True

b) False

Answer: b

Explanation: In discharge of water over narrow crested weir, head of water is inversely proportional to Discharge Coefficient.

2. In discharge of water over narrow crested weir, discharge is directly proportional to the cube root of acceleration due to gravity.

a) True

b) False

Answer: b

Explanation: In discharge of water over narrow crested weir, discharge is directly proportional to the square root of acceleration due to gravity.

3. In discharge of water over ogee weir, discharge is directly proportional to the second power of length.

a) True

b) False

Answer: b

Explanation: In discharge of water over ogee weir, discharge is directly proportional to the first power of length.

4. For discharge over ogee weir discharge is directly proportional to length but for discharge over narrow crested weir it is inversely proportional to length.

a) True

b) False

Answer: b

Explanation: For both weirs it’s same.

5. An Ogee weir 5 m long had a head of 40 cm of water. If CD = 0.61, find the discharge over the weir.

a) 2.9 m 3 /s

b) 2.3 m 3 /s

c) 3.1 m 3 /s

d) 3.3 m 3 /s

Answer: a

Explanation: Q = 0.67 * Cd * L * √2g * H 1.5

Q = 2.3 m 3 /s.

6. The height of water on upstream and downstream side of a submerged weir of 4 m length are 24 cm and 13 cm. If Cd for free and drowned portions are .62 and .78 respectively, find the discharge over the weir.

a) .85 m 3 /s

b) 1.35 m 3 /s

c) 3.2 m 3 /s

d) .55 m 3 /s

Answer: a

Explanation: Q = 0.67 * Cd1 * L * √2g * H 1.5 +. Cd2 * L * h * √2g

= .67 * .6 * 3 * √2g *  1.5 + .8 * 3 * .13 √2g

= .85 m 3 /s.

7. An Ogee weir 3.4 m long had a head of 40 cm of water. If CD = 0.63 find the discharge over the weir.

a) 1.61 m 3 /s

b) 2.5 m 3 /s

c) 3.1 m 3 /s

d) 3.3 m 3 /s

Answer: a

Explanation: Q = 0.67 * Cd * L * √2g * H 1.5

Q = 1.61 m 3 /s.

8. The height of water on upstream and downstream side of a submerged weir of 4 m length are 23.5 cm and 14 cm. If Cd for free and drowned portions are .61 and .75 respectively, find the discharge over the weir.

a) m 3 /s

b) 1.35 m 3 /s

c) 3.2 m 3 /s

d) .55 m 3 /s

Answer: a

Explanation: Q = 0.67 * Cd1 * L * √2g * H 1.5 +. Cd2 * L * h * √2g

= .67 * .6 * 3 * √2g *  1.5 + .8 * 3 * .13 √2g

= .85 m 3 /s.

9. In discharge of water over narrow crested weir, discharge is directly proportional to the second power of height.

a) True

b) False

Answer: b

Examples: In discharge of water over narrow crested weir, discharge is directly proportional to the one and half power of height.

10. In discharge of water over Ogee weir, discharge is directly proportional to the first power of length.

a) True

b) False

Answer: a

Explanation: This is as per empirical relation.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Shear Stress and Pressure Gradient”.

1. What is the unit of shear stress?

a) N/m 3

b) N/mm 3

c) N/m

d) Pascal

Answer: d

Explanation: Shear stress is defined as the force acting per unit area. Thus, the unit of shear stress is equal to N/m 2 . Since, 1 Pa =1 N/m 2 , Pascal is the most suitable one.

2. Shear stress is caused due to _______

a) Friction

b) Temperature

c) Pressure

d) Volume

Answer: a

Explanation: Shear stress is caused due to friction between fluid particles. It is formed due to the presence of fluid viscosity. Shear stress arises from the force vector component which is parallel to the cross section.

3. Which among the following is a formula for shear stress?

a) τ = F*A

b) τ = F/A

c) τ = F/m

d) τ = F*m

Answer: b

Explanation: Shear stress is defined as the force acting per unit area. Shear stresses arise from shear components, which are pairs of equal and opposite forces. These forces act on the opposite side of the object.

4. Which among the following is the correct formula to find out the shear modulus?

a) E/2

b) v/2

c) E/2

d) 2E

Answer: c

Explanation: Shear modulus is also called as modulus of rigidity. It is defined as the ratio of shear stress to shear strain. Since Young modulus is equal to stress by strain. The most suitable option is option c. 

5. Which among the following is an assumption of Hagen-Poiseuille equation?

a) Fluid is compressible

b) Fluid is uniform

c) Fluid is laminar

d) Fluid is turbulent

Answer: c

Explanation: Fluid flow is laminar as it is assumed to be incompressible and Newtonian. The flow is laminar through the pipe of constant cross section. Thus, there is no acceleration of fluid in the pipe. Therefore, Hagen-Poiseuille assumed that fluid flow is laminar.

6. What is the unit of pressure gradient?

a) Pa/m

b) Nm

c) Pa

d) N/m

Answer: a

Explanation: Pressure gradient is a dimensional quantity. It is expressed in units of pressure per unit length. It determines which quantity and which direction the pressure changes around a particular location.

7. Which of the following is not a basic type of stress?

a) Volumetric stress

b) Shear stress

c) Compressive stress

d) Tensile stress

Answer: a

Explanation: Volumetric stress is not a basic classification among the type of stresses as it describes the tendency of an object to deform in all directions. It deforms when the load acts uniformly in all directions.

8. What type of force does a stress produce?

a) Radial force

b) External force

c) Internal resistive force

d) Axial force

Answer: c

Explanation: According to the continuum mechanics, stress is a physical quantity that produces internal forces. For example: When a solid bar supports a weight, each particle of the bar pushes the particles immediately below it. This happens due to the internal resistive force that is developed due to the stress on the body.

9. Hooke’s law is applicable within what limit?

a) Fracture point

b) Elastic limit

c) Ultimate strength

d) Plastic limit

Answer: b

Explanation: Hooke’s law states that force is directly proportional to its extension. Hooke’s law is applicable within the elastic limit, when the body is deformed. Example: plucking the strings of a guitar.

10. Define Factor of safety

a) Ultimate stress/Permissible stress

b) Ultimate stress/ Shear stress

c) Compressive stress/ Ultimate stress

d) Tensile stress/Shear stress

Answer: a

Explanation: Factor of safety determines the maximum load carrying capacity. It tells us how much stronger the system is than it usually needs to be for a particular specified load. It is the ratio of allowable stress to the actual stress.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Flow of Viscous Fluid Through Circular Pipes”.

1. For a fully-developed pipe flow, how does the pressure vary with the length of the pipe?

a) Linearly

b) Parabolic

c) Exponential

d) Constant

Answer: a

Explanation: In a zero acceleration fully-developed flow in a pipe, the pressure gradually decreases linearly along the length of the pipe. Hence, the pressure variation is said to be linear.

2. When a problem states “The velocity of the water flow in a pipe is 20 m/s”, which of the following velocities is it talking about?

a) RMS velocity

b) Average velocity

c) Absolute velocity

d) Relative velocity

Answer: b

Explanation: In a pipe-flow, the velocity is always referred to the average velocity. There may be a case where all water particles move in the same direction with 20 m/s, then the average velocity will be equal to absolute velocity. But, this is only a special case. Hence, average velocity will always be true.

3. Which of the factors primarily decide whether the flow in a circular pipe is laminar or turbulent?

a) The Prandtl Number

b) The Pressure gradient along the length of the pipe

c) The dynamic viscosity coefficient

d) The Reynolds Number

Answer: d

Explanation: High Reynolds number flows  are turbulent flows, whereas low Reynolds number flows  are laminar flows. The viscosity coefficient is a part of the Reynolds number, but isn’t the only criteria for decision.

4. How is Reynolds number defined as?

a) Ratio of pressures in the inlet to the outlet of a pipe

b) The product of velocity of the flow and the diameter of the pipe, divided by the kinematic viscosity of fluid

c) The product of density of the fluid, velocity of the flow and the diameter of the pipe, divided by the dynamic viscosity of fluid

d) Ratio of inertia force to viscous force

Answer: d

Explanation: The question demands the definition and not the commonly used formula of Reynolds number. Some of them denote the formula of Reynolds number. The definition of Reynolds number is the ratio of inertia force to viscous force in a pipe flow.

5. A circular pipe of radius 7 cm is used for water flow transmission. This pipe is moulded into another pipe with a square cross-section keeping the length same. . Calculate the hydraulic diameter of the moulded pipe. .

a) 11 cm

b) 7 cm

c) 3.5 cm

d) 22 cm

Answer: a

Explanation: The perimeter of the circular cross section and the square cross section will remain the same. Perimeter = 44 cm. Side of square = 11 cm. Hydraulic diameter DH of the pipe is given by 4A/P, where A = Area of cross section and P = wetted perimeter. In case of a square DH = side. Hence, the hydraulic diameter is 11 cm.

6. Water flows through a circular tube with a velocity of 2 m/s. The diameter of the pipe is 14 cm. Take kinematic viscosity of water 10 -6 m 2 /s and density of water 1000 kg/m 3 .

a) 2.8*10 8

b) 2.8*10 5

c) 2800

d) 28000

Answer: b

Explanation: Reynolds number is given by VD/ν = /10 -6 . Density given is extra information. One shouldn’t be confused by that.

7. The Reynolds number is found out for a flow in a circular pipe. This circular pipe is moulded into a square pipe, keeping length of the pipe same. Ignore the thickness of the pipe. The Reynolds number changes by __________

a) 57% decrease

b) 57% increase

c) 43% decrease

d) 43% increase

Answer: b

Explanation: The Reynolds number directly depends upon the hydraulic diameter of the pipe. Suppose the diameter of the pipe is D, the hydraulic diameter of square pipe is 1.57D. Hence, 57% increase.

8. The flow through a circular pipe is laminar. Now, the fluid through the pipe is replaced with a more viscous fluid and passed through the pipe again with the same velocity. What can we say about the nature of this flow?

a) The flow will become turbulent

b) The flow will be a transition flow

c) The flow will remain laminar

d) The Reynolds number of the earlier flow is required to answer this question

Answer: c

Explanation: A flow through a circular pipe is said to be laminar when the Reynolds number is below 2100. A more viscous fluid would have a higher velocity coefficient, thus reducing the Reynolds number further at the same conditions. Hence, the Reynolds number will be well below 2100. Flow will remain laminar.

9. What can be the maximum diameter of the pipe for the water flow of velocity 1 m/s (ν = 10 -6 ) to be laminar in nature? Assume Lower critical Reynolds number to be 2100.

a) 2.1 mm

b) 21 mm

c) 21 cm

d) 0.21 mm

Answer: a

Explanation: If the Reynolds number of the flow is below its lower critical Reynolds number, the flow is clearly laminar. The maximum diameter can be found for Re = 2100. The diameter comes out to be 2.1 mm.

10. Which of the following flows have the highest critical Reynolds number ?

a) Flow in a pipe

b) Flow between parallel plates

c) Flow in an open channel

d) Flow around spherical body

Answer: a

Explanation: The approximate lower critical Reynolds number for Flow in a pipe, flow between parallel plates, flow in an open channel and flow around the spherical body are 2000, 1000, 500 and 1 respectively. Hence, the maximum is for internal pipe flow.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Kinetic Energy Correction and Momentum Correction Factors”.

1. What is the value of kinetic energy factor during a laminar flow?

a) 1

b) 2

c) 3

d) 4

Answer: b

Explanation: Kinetic energy factor for a fully developed laminar flow is around 2. Laminar flow occurs when a fluid flows in parallel layers. The flow must not have any sort of disruption between the layers of fluid. The fluid flows without a lateral mixing which makes it slide past one another.

2. Which among the following is not an application of the Bernoulli?

a) Sailing

b) Flow through a venture tube

c) Flow through a sharp-edged orifice.

d) Closing of tap water

Answer: b

Explanation: This is mainly because, Bernoulli’s equation is applied only when the fluid is irrotational. It means that the stream lines are not supposed to intersect each other. Also, the equation does not take viscosity into account. Thus, the flow rate decreases when you close the valve.

3. If you double the kinetic energy of an arrow, by what factor does its speed increase?

a) 2

b) 4

c) same

d) √2

Answer: d

Explanation: Kinetic energy depends upon velocity and mass. The relation between K.E with mass and velocity is K.E= 0.5mv 2 . If we double the kinetic energy, the velocity has to be increased by a factor equal to the square root of two.

4. What is the function of Reynolds number?

a) To detect pressure changes

b) To predict flow patterns

c) Temperature

d) Viscosity

Answer: b

Explanation: Reynolds number is a dimensionless quantity. It is used to predict flow patterns in different types of fluid flow. At lower Reynold’s number, the flow is laminar. At higher Reynolds number, the flow is turbulent.

5. When a bullet hits a solid block and gets embedded into it. What is conserved?

a) Momentum only

b) Kinetic energy only

c) Momentum and kinetic energy

d) Mass

Answer: a

Explanation: When the bullet is released from the gun, it moves through the individual air molecules. These molecules tend to vibrate which cannot be seen though our naked eye. The solid block acts as a “momentum sink”. It’s so big when compared to a tiny bullet that it can absorb all the momentum without visibly moving.

6. If the kinetic energy is increased 4 times its initial value, then how does its momentum change?

a) 100%

b) 50%

c) 200%

d) 150%

Answer: a

Explanation: Kinetic energy depends upon velocity and mass. The relation is K.E= 0.5mv 2 . If we increase the kinetic energy by 4 times its initial value, the momentum has to be increased by 100% its initial value.

7. When a charged body enters a uniform magnetic field. How will it’s kinetic energy change?

a) Doubles

b) 4 times

c) Constant

d) Triples

Answer: c

Explanation: The kinetic energy remains a constant as the magnetic field always exerts a force perpendicular to the particle’s velocity. So, there is no change in the velocity of the fluid. Therefore, kinetic energy remains the same.

8. What is the relation between kinetic energy and momentum?

a) p=m/v

b) p=mva

c) p=mv

d) p=m

Answer: c

Explanation: Kinetic energy depends upon velocity and mass. The relation is K.E= 0.5mv 2 . The momentum of the body=mv. Now, equating the two we get, K.E=0.5mv 2 =p 2 /2m. Therefore, the relation between kinetic energy and momentum is .

9. How can you slow down a fast neutron?

a) Applying an electric field

b) Using shield

c) Elastic collision

d) Heavy water

Answer: d

Explanation: The fast neutrons are converted to thermal neutrons when they are passed through heavy water(D 2 O). The key factor for the neutrons to slow down are its atomic number. The velocity of the fast neutrons decreases with a few collisions.

10. If a cricket ball moves with a velocity ‘v’ and collides with a tiny table tennis ball. After an elastic collision, at what velocity will the second ball move?

a) v

b) v/2

c) 2v

d) v 2

Answer: c

Explanation: Since the collision is elastic, the cricket ball having a higher mass than that of the tiny table tennis ball will hit and generate a higher velocity. After immediate impact, the table tennis ball will move exactly with twice the velocity of the cricket ball.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Power Absorbed in Viscous Flow”.

1. During which case will the power loss be maximum?

a) High viscosity oil

b) Low viscosity oil

c) High viscosity water

d) Low viscosity water

Answer: a

Explanation: A highly viscous oil will offer greater resistance due to which the power loss is maximum. As we know, oil has a greater density than water. Thus, oil is more viscous than water and corresponds to a higher loss of power.

2. Angular speed of the shaft is________

a) 2πN/1000

b) 2πN/60

c) 2π/N

d) 2N/60

Answer: b

Explanation: Angular speed is defined as the rate at which an object changes its angles. The angle can be measured in radians. Angular speed is a scalar quantity. It is measured within a given time period.

3. Tangential speed of the shaft is______

a) 2πN/1000

b) πDN/1000

c) πDN/60

d) 2πN/60

Answer: c

Explanation: Tangential speed is defined as the distance travelled per unit time. It is a linear speed of something that moves around a circular path. Example of tangential speed is a point on the edge of a merry-go-round. The merry-go-round travels a greater distance in one complete rotation than the point near the centre.

4. Fluid does not offer resistance to change of__________

a) Temperature

b) Volume

c) Pressure

d) Shape

Answer: d

Explanation: Shape is one of the most important factors for a fluid. The forces other than gravity that fall on the fluid affects the outcome. Thus, changing the shape of the fluid cannot be controlled.

5. If a fluid does not undergo any sort of resistance by displacement. What substance is it called?

a) Ideal fluid

b) Solid

c) Gas

d) Water

Answer: a

Explanation: An ideal fluid is a fluid that has zero viscosity. It results in a flow called as inviscid flow. In this flow there is no existence of shear force and the viscosity vanishes.

6. Why can’t mercury wet a glass?

a) Cohesion

b) Adhesion

c) Surface tension

d) Compressibility

Answer: c

Explanation: Surface tension is an elastic tendency of a fluid. It results due to imbalance of intermolecular attractive forces. Any molecule at the surface of the liquid experiences a net inward force. Mercury having a higher density than water, cannot wet a glass.

7. What is the unit of power absorbed in a fluid?

a) Ampere

b) Volt/m

c) kgm 2 s -3

d) kg/m

Answer: c

Explanation: Unit of power is a Watt. This is in accordance with the SI unit. The International system of units define it as 1 joule per second. Therefore, the SI base unit is kgm 2 s -3 . It was named after James Watt.

8. One horse power is__________

a) 7460 W

b) 746 kW

c) 746 W

d) 0.746 W

Answer: c

Explanation: Horse power is defined as the unit of foot-pound-second. Foot-pound-second is a unit in accordance with the English system. One horse power is equal to 550 fps/s. Thus, the power relation is 1HP= 746W.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Loss of Head due to Friction in Viscous Flow”.

1. Which among the following does not depend on the friction factor?

a) Pipe diameter

b) Fluid density

c) Viscosity

d) Weight

Answer: d

Explanation: The friction factor depends on the velocity of flow, fluid density, pipe diameter and the viscosity of the pipe. Roughness of the pipe is also an important criteria to determine the friction factor.

2. Which among the following is the formula for friction factor?

a) f = 0.079*Re 0.25

b) f = 0.079/Re 0.25

c) f = 0.079/Re 0.5

d) f = 0.079*Re 0.5

Answer: b

Explanation: To calculate the friction factor of a fluid, we use the Blasius equation. This equation is accurate for values within 5% having Reynolds number less than 10 5 . (Blasius equation: f= 0.079/Re 0.25 )

3. How do we calculate losses for a larger range of Reynolds number?

a) Moody chart

b) Bar chart

c) Scatter chart

d) Column histogram

Answer: a

Explanation: Moody chart is a graph of frictional factor vs Reynolds numbers. It gives various values corresponding to the ‘k/d’ ratios. Where ‘k’ is the measure of the wall roughness and ‘d’ is the pipe diameter.

4. Darcy- Weisbach equation gives relation between__________

a) Pressure and temperature

b) Mass, volume and pressure

c) Head loss and pressure loss

d) Pressure loss only

Answer: c

Explanation: Darcy-Weisbach equation relates the head loss and pressure loss due to friction along a given pipe with a specified length. It contains a dimensionless friction factor called the Darcy friction factor. The equation was named after Henry Darcy and Julius Weisbach.

5. Which among the following is formula for friction factor of circular pipes?

a) 16/Re

b) 64/Re

c) Re/16

d) Re/64

Answer: b

Explanation: Circular pipes have a diameter treated in a round manner. For a fluid flow which is laminar head loss is directly proportional to the fluid velocity. Thus, friction factor is inversely proportional to its velocity. Therefore, the correct option is ‘64/Re’.

6. Loss of head due to friction is __________

a) Directly proportional to hydraulic radius

b) Inversely proportional to velocity

c) Inversely proportional to hydraulic radius

d) Directly proportional to gravitational constant

Answer: c

Explanation: Hydraulic radius is one of the properties of a fluid flow in a channel. It controls the water discharge. It also determines the amount of work the channel can do. (R h =A/P). Thus, it is inversely proportional to loss of head due to friction.

7. The formula for hydraulic diameter is______

a) 4A/P

b) 4AP

c) 4AV

d) 4V

Answer: a

Explanation: Hydraulic diameter handles the flow in non-circular channels and tubes. The most suitable term to calculate the hydraulic diameter for a round tube is D h = 4A/P. Where ‘A’ is the cross-sectional area and ‘P’ is the wetted perimeter.

8. What are the reasons for minor head loses in a pipe?

a) Friction

b) Heat

c) Valves and bends

d) Temperature

Answer: c

Explanation: Minor losses play an important role in calculating the flow, pressure and energy of the piping system. Fluid that moves through the pipe carries momentum and energy due to the forces acting on them. Thus, these minor loses are developed due to valves, pipe diameter and bending.

9. What happens to the head loss when the flow rate is doubled?

a) Doubles

b) Same

c) Triples

d) Four times

Answer: d

Explanation: If the flow rate is doubled, the head loss increases by a factor of four. Since, the head loss is directly proportional to the square of the flow rate. Option  is the correct option.

10. Relative roughness is_________

a) ϵ/D

b) ϵ*D

c) ϵ/Dm

d) ϵgD

Answer: a

Explanation: Relative roughness is defined as the quantity used to measure the roughness of the pipe’s surface. It is equal to the average height of the surface irregularities divided by the pipe diameter. Therefore, Relative roughness= ϵ/D.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Movement of Piston in Dash Pot”.

1. The dashpot timer is_______

a) Manual

b) Automatic

c) Controlled

d) Free Movement

Answer: b

Explanation: The dashpot timer is an automatic timer. It is used in several machines and has ‘n’ number of variations. It is used in many applications such as printing presses, generating motors and in many irrigation systems.

2. Mechanical timers measure time using______

a) Thermal Mechanism

b) Computer code

c) Clock

d) Glass

Answer: c

Explanation: Mechanical timers use clock to measure time intervals. It can be categorised into two types. One of them is a stop watch, which measures the elapsed time and the other is an hourglass. Both these methods follow the same principle of recording the time intervals.

3. Which among the following is an oldest mechanical timer?

a) Stop watch

b) Egg-timers

c) Balance wheel

d) Hour glass

Answer: d

Explanation: Hour glass is a device that is used to measure the passage of time. An hour glass contains two glass bulbs connected by a narrow neck. This allows a trickle of material from the upper bulb to the lower one. .

4. Electronic timers are essentially ________

a) Quartz clock

b) Stop watch

c) Hour glass

d) Egg-timers

Answer: a

Explanation: Electronic timers are quartz clocks. They are modified with special electronics. They can achieve higher precision when compared to mechanical timers. Electronic timers work on digital electronics which have analog or digital display.

5. Software timers work on__________

a) Quartz glass

b) Balance wheel

c) Computer code

d) Liquid

Answer: c

Explanation: Software timers are not devices or parts of devices. They work on computer code which relies on the accuracy of a clock generator. It is usually built into a hardware device that runs on the principle of software.

6. What type of device is a dashpot?

a) Electronic

b) Mechanical

c) Thermal

d) Computerised

Answer: b

Explanation: A dashpot contains a damper which resists the motion with the help of a viscous flow. The force so produced is directly proportional to the velocity. But, it acts in the opposite direction, thus slowing the motion and absorbing the energy. By this way, the dashpot works on a mechanical basis.

7. What are the types of dashpot?

a) Linear and rotary

b) Reciprocating and nonuniform.

c) Linear and reciprocating

d) Circular and rotational

Answer: a

Explanation: Dashpot is divided into two types, linear and rotary types. Linear dashpots are specified by the amount of linear displacement  and force per velocity . Rotary dashpots will have force per velocity in torque so developed.

8. Which among the following is not an application of the dashpot?

a) Door closer

b) Consumer electronics

c) Timers

d) Pilot Static Tube

Answer: d

Explanation: Pilot static tube is a system that uses an automatic control scheme to detect pressure. It has several holes connected to one side of the device. These outside holes are called as a pressure transducer, which controls the automatic scheme during fluid flow.

9. Example of amorphous substance is _______

a) Polymers

b) Diamond

c) Snowflakes

d) Quartz

Answer: a

Explanation: Amorphous substances are substances that have an internal structure. These internal structures are made up of interconnected structural blocks. They have a long-range order. A good example of an amorphous substance is a polymer.

10. Which among the following is not a type of crystalline substances?

a) Ionic

b) Metallic

c) Covalent

d) Hydrogen bond

Answer: d

Explanation: A crystalline substance does not undergo hydrogen bonding. A crystalline substance is a substance in which the constituents are arranged in a highly ordered microscopic structure. It forms a crystal lattice in all directions.

11. Fluid sealing in a dashpot is achieved using________

a) Circlips

b) Piston rings

c) Flakes

d) Quartz

Answer: b

Explanation: Fluid sealing in a dashpot is achieved using a piston ring. Piston rings are a number of narrow iron rings which are fitted loosely into the grooves of the piston. The rings split at a point on the rim which is placed just below the crown.

12. Which among the following is the best suitable material for making a piston?

a) Hiduminium

b) Titanium

c) Aluminium

d) Borium

Answer: c

Explanation: Pistons are made from aluminium alloys. The properties of these alloys can be improved by forging technique. Forging is done to improve the fatigue life and strength of the piston.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Universal Velocity Distribution”.

1. What is an aspect ratio in universal velocity distribution?

a) b*h

b) b/h

c) b+h

d) b-h

Answer: b

Explanation: Aspect ratio in universal velocity ratio is defined as the ratio of free surface of the fluid flow width to the depth of water. The formula is : Aspect ratio= b/h. It can also be defined as the ratio of span to the mean chord in an aero foil.

2. What is the ratio of maximum velocity to the average velocity when the fluid passes through two parallel plates?

a) 1/4

b) 1/2

c) 3/4

d) 1

Answer: c

Explanation: The maximum velocity occurs at the centre. At the centre, the radius is equal to zero. The average velocity is obtained by dividing the discharge of fluid. The discharge takes place across the cross-sectional area of the pipe.

3. The Prandtl Number approximates ___________

a) Momentum diffusivity to thermal diffusivity

b) Thermal diffusivity to momentum diffusivity

c) Shear stress to thermal diffusivity

d) Thermal diffusivity to kinematic viscosity

Answer: a

Explanation: The Prandtl number is a dimensionless number. It approximates the ratio of momentum diffusivity to thermal diffusivity. It can be expressed as P r = v/ α. Where α= thermal diffusivity and v = momentum diffusivity.

4. Eddy viscosity is a turbulent transfer of_________

a) Fluid

b) Heat

c) Momentum

d) Pressure

Answer: c

Explanation: Eddy viscosity is a turbulent transfer of momentum by eddies. It gives rise to an internal fluid friction. It is in analogous to the action of molecular viscosity in a laminar fluid flow. Eddy viscosity takes place on a large scale.

5. What is the function of transilient turbulence theory?

a) Parameterizing turbulence

b) Stopping turbulence

c) Initiating turbulence

d) Detecting turbulence

Answer: a

Explanation: Transilient turbulence theory is the method used for parameterizing turbulence. Its main function is to allow all non-local vertical mixing between every pair of grid points. It happens in mainly in the vertical column.

6. What is the formula for kinematic eddy viscosity?

a) Eddy viscosity / kinematic viscosity

b) Eddy viscosity * kinematic viscosity

c) Eddy viscosity / mass density

d) Eddy viscosity / dynamic viscosity

Answer: c

Explanation: Kinematic eddy viscosity is defined as the ratio between Eddy viscosity and mass density of the fluid. It happens mainly at one hundred times the molecular kinematic viscosity. It is in the order 1m 2 s -1 .

7. Eddy diffusion happens due to_________

a) Eddy motion

b) Fluid motion

c) Water constraint

d) Eddy constraint

Answer: a

Explanation: Eddy diffusion happens due to Eddy motion. This eddy motion is created due to fluid mixing. The fluid mixture causes the formation of eddies. Eddies can vary in size from small microscales to subtropical scales.

8. When is the fluid called laminar?

a) Reynolds number is greater than 2000

b) Reynolds number is less than 2000

c) The density of the fluid is high

d) Low viscosity

Answer: b

Explanation: Reynolds number is a dimensionless quantity. It helps to predict the flow pattern in fluid mechanics. At low Reynolds number, the flow has a very low density, due to which the value of Reynolds number is less than 2000.

9. When is a fluid called turbulent?

a) Reynolds number is greater than 2000

b) Reynolds number is less than 2000

c) The density of the fluid is low

d) High viscosity of fluid

Answer: a

Explanation: Reynolds number is a dimensionless quantity. It helps to predict the flow pattern in fluid mechanics. At high Reynolds number, the flow has a very high density, due to which the value of Reynolds number is greater than 2000.

10. Coefficient of friction of a laminar flow is_________

a) R e /16

b) R e /64

c) 16/R e

d) 64/R e

Answer: c

Explanation: Coefficient of friction is defined as the value that shows relationship between force and the normal reaction. It is mainly used to find out an object’s normal force and frictional force. Thus, it is equal to 16/R e .

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Methods of Determination of Coefficient of Viscosity”.

1. What is the unit of coefficient of viscosity?

a) kgsm -2

b) kgms -2

c) Nms -2

d) Nsm -2

Answer: d

Explanation: Coefficient of viscosity is defined as the degree to which the fluid resists flow under an applied force. It is expressed as ratio of shearing stress to the velocity gradient. The unit is Nsm -2 .

2. What happens to the coefficient of viscosity if the temperature increases?

a) Increases

b) Decreases

c) Remains the same

d) Independent of temperature

Answer: b

Explanation: With the increase in temperature, the coefficient of viscosity of fluid decreases. This happens due to the weakening of bonds between the molecules. Because of its dash pot coefficient, the flow attains peak deformation.

3. What is the magnitude of the coefficient of viscosity?

a) Frictional force/Area

b) Frictional force/ 

c) Frictional force*Area

d) Frictional force*Area/ velocity gradient

Answer: b

Explanation: Coefficient of viscosity is defined as the degree to which the fluid resists flow under an applied force. It is expressed as a ratio of shearing stress to the velocity gradient. It has a unit of Nsm -2 .

4. Which among the following methods are not standard laboratory viscometers?

a) Saybolt Viscometer

b) Redwood Viscometer

c) Ostwald Viscometer

d) Vibrational viscometer

Answer: d

Explanation: Vibrational viscometer is a viscometer that serves the same purpose as the other viscometers. But, it is not used for laboratory purposes. It measures the damping oscillations using a resonator immersed in a fluid.

5. What is the formula for coefficient of static friction?

a) R/F

b) F*R

c) F/R

d) F+R

Answer: c

Explanation: Coefficient of static friction is defined as the ratio of limiting frictional force to the normal reaction force. Limiting frictional force is denoted by ‘F’ and normal frictional force is denoted by ‘R’. Therefore, option ‘c’ is correct.

6. What is the dimension for coefficient of friction?

a) [M][L][T]

b) [M][L][T] 2

c) It has no dimensions

d) [M][L] -1 [T] -1

Answer: c

Explanation: Coefficient of static friction is defined as the ratio of limiting frictional force to the normal reaction force. Dividing the dimensions of the limiting frictional force and normal frictional force, the units cancel out each other due to which it has no dimensions.

7. Where is friction a drawback?

a) On roads

b) On pipes

c) Staircase

d) Playground

Answer: b

Explanation: Friction in pipes lead to major and minor loses. It is an economic significance. It provides a lot of confusions on whether the pipe or duct is entirely closed. It leads to a high amount of power loss in drawing fluid through the pipes.

8. Measuring the coefficient of static friction takes place by_________

a) Tilting two objects

b) Keeping it stationery

c) Reciprocating

d) Rotating

Answer: a

Explanation: The easiest way to measure the coefficient of static friction is by placing the two objects together and tilting them until one object slides over the other. Coefficient is related to the angle at which one object starts to slide over the other.

9. Coefficient of kinetic friction can be found out by inclined plane method and horizontal plane method.

a) True

b) False

Answer: a

Explanation: Coefficient of kinetic friction can be found out by inclined plane method and horizontal plane method. In case of inclined plane, the block slides down on an incline with a constant velocity. In the horizontal plane method, the block does not slide and produces nil friction.

10. Which among the following is used to determine the angle of repose?

a) Horizontal plane method

b) Tilting box method

c) Fixed funnel method

d) Revolving cylinder method

Answer: a

Explanation: Angle of repose is defined as the steepest angle of descent or dip. It is with relation to the horizontal plane to which a material can be piled. Example: When we pile up stones one over the other, the stones tend to slide along the heap at a certain point. The angle at that point is the angle of repose.

11. What is the maximum value for the angle of repose?

a) 30

b) 60

c) 90

d) 180

Answer: c

Explanation: Angle of repose is defined as the steepest angle of descent or dip. It is with relation to the horizontal plane to which a material can be piled. The maximum value for the angle of repose is 90 degrees. It is exactly perpendicular to the horizontal surface.

12. What is the minimum value for angle of repose?

a) 0

b) 60

c) 90

d) 180

Answer: a

Explanation: Angle of repose is defined as the steepest angle of descent or dip. It is with relation to the horizontal plane to which a material can be piled. The minimum value for angle of repose is zero degrees. It lies on the horizontal surface. Therefore, there is no sliding.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Loss of Energy in Pipes”.

1. Which one of the following is a major loss?

a) frictional loss

b) shock loss

c) entry loss

d) exit loss

Answer: a

Explanation: The major loss for the flflow through the pipes is due to the frictional resistance between adjacent fluid layers sliding over each other. All other losses are considered to be minor losses.

2. Which property of the fluid accounts for the major losses in pipes?

a) density

b) specific gravity

c) viscosity

d) compressibility

Answer: c

Explanation: The major loss for the flow through the pipes is due to the frictional resistance between adjacent fluid layers sliding over each other. This resistance arises due to the presence of viscous property of the fluid.

3. The frictional resistance for fluids in motion is

a) proportional to the velocity in laminar flow and to the square of the velocity in turbulent flow

b) proportional to the square of the velocity in laminar flow and to the velocity in turbulent flow

c) proportional to the velocity in both laminar flow and turbulent flow

d) proportional to the square of the velocity in both laminar flow and turbulent flow

Answer: a

Explanation: According to the laws of fluid friction, r f / v  and r f / v2, where rf is the frictional resistance and v is the velocity of flow.

4. The frictional resistance for fluids in motion is

a) dependent on the pressure for both laminar and turbulent flows

b) independent of the pressure for both laminar and turbulent flows

c) dependent on the pressure for laminar flow and independent of the pressure for turbulent flow

d) independent of the pressure for laminar flow and dependent on the pressure for turbulent flow

Answer: b

Explanation: According to the laws of fluid friction, the frictional resistance is independent of the pressure for both laminar and turbulent flows.

5. The frictional resistance for fluids in motion is

a) inversely proportional to the square of the surface area of contact

b) inversely proportional to the surface area of contact

c) proportional to the square of the surface area of contact

d) proportional to the surface area of contact

Answer: d

Explanation: According to the laws of fluid friction, the frictional resistance is proportional to the surface area of contact for both laminar and turbulent flows.

6. The frictional resistance for fluids in motion varies

a) slightly with temperature for both laminar and turbulent flows

b) considerably with temperature for both laminar and turbulent flows

c) slightly with temperature for laminar flow and considerably with temperature for turbulent flow

d) considerably with temperature for laminar flow and slightly with temperature for turbulent flow

Answer: d

Explanation: According to the laws of fluid friction, the frictional resistance for fluids in motion varies considerably with temperature for laminar flow and slightly with temperature for turbulent flow.

7. Which one of the follflowing is correct?

a) the frictional resistance depends on the nature of the surface area of contact

b) the frictional resistance is independent of the nature of the surface area of contact

c) the frictional resistance depends on the nature of the surface area of contact for laminar flows but is independent of the nature of the surface area of contact for turbulent flows

d) the frictional resistance is independent of the nature of the surface area of contact for laminar flows but depends on the nature of the surface area of contact for turbulent flows

Answer: d

Explanation: According to the laws of fluid friction, the frictional resistance is independent of the nature of the surface area of contact for laminar flows but depends on the nature of the surface area of contact for turbulent flows.

8. Which one of the follflowing is correct?

a) the frictional resistance is always dependent on the nature of the surface area of contact

b) the frictional resistance is always independent of the nature of the surface area of contact

c) the frictional resistance is dependent on the nature of the surface area of contact when the liquid flows at a velocity less than the critical velocity

d) the frictional resistance is independent of the nature of the surface area of contact when the liquid flows at a velocity less than the critical velocity

Answer: d

Explanation: Frictional resistance is dependent on the nature of the surface area of contact. But, when the liquid flows at a velocity less than the critical velocity, a thin stationary film of the liquid is formed on the supporting surface. Hence, the frictional resistance becomes independent of the nature of the surface of contact.

9. Which one of the follflowing is correct?

a) Darcy-Weisbach’s formula is generally used for head loss in flow through both pipes and open channels

b) Chezy’s formula is generally used for head loss in flow through both pipes and open channels

c) Darcy-Weisbach’s formula is generally used for head loss in flow through both pipes and Chezy’s formula for open channels

d) Chezy’s formula is generally used for head loss in flow through both pipes and Darcy-Weisbach’s formula for open channels

Answer: c

Explanation: Darcy-Weisbach’s formula is generally used for head loss in flow through both pipes as it takes into consideration the flow velocity whereas Chezy’s formula is used for open channels as it considers the pressure difference.

10. A liquid flows through pipes 1 and 2 with the same flow velocity. If the ratio of their pipe diameters d 1 : d 2 be 3:2, what will be the ratio of the head loss in the two pipes?

a) 3:2

b) 9:4

c) 2:3

d) 4:9

Answer: c

Explanation: According to Darcy-Weisbach’s formula,

fluid-mechanics-questions-answers-loss-head-pipes

whereh f is the head loss in the pipe, f is the co-efficient of friction, L is the length, D is the diameter and V is the flow velocity. Thus, h f1 : h f2 = D 2 : D 1 = 2 : 3.

11. A liquid flowss through two similar pipes 1 and 2. If the ratio of their flow velocities v1 : v2 be 2:3, what will be the ratio of the head loss in the two pipes?

a) 3:2

b) 9:4

c) 2:3

d) 4:9

Answer: d

Explanation: According to Darcy-Weisbach’s formula,

fluid-mechanics-questions-answers-loss-head-pipes

where h f is the head loss in the pipe, f is the co-efficient of friction, L is the length, D is the diameter and V is the flow velocity. Thus, h f1 : h f2 = v1 : v2 = 4 : 9.

12. A liquid flows with the same velocity through two pipes 1 and 2 having the same diameter. If the length of the second pipe be twice that of the first pipe, what should be the ratio of the head loss in the two pipes?

a) 1:2

b) 2:1

c) 1:4

d) 4:1

Answer: a

Explanation: According to Darcy-Weisbach’s formula,

fluid-mechanics-questions-answers-loss-head-pipes

where h f is the head loss in the pipe, f is the co-efficient of friction, L is the length, D is the diameter and V is the flow velocity. Thus, h f1 : h f2 = L1 : L2 = 1 : 2.

13. The head loss at the entrance of the pipe is that at it’s exit

a) equal to

b) half

c) twice

d) four times

Answer: b

Explanation: According to Darcy-Weisbach’s formula,

fluid-mechanics-questions-answers-loss-head-pipes

h i = o.5v 2 / 2g and ho = v 2 / 2g, where h i is the head loss at pipe entrance, h o is the head loss at pipe exit and v is the flow velocity. Thus h i = 0.5h o .

14. On which of the factors does the co-efficent of bend in a pipe depend?

a) angle of bend and radius of curvature of the bend

b) angle of bend and radius of the pipe

c) radius of curvature of the bend and pipe

d) radius of curvature of the bend and pipe and angle of bend

Answer: d

Explanation: The co-efficent of bend in a pipe depends on all the three parameters – radius of curvature of the bend, diameter  of the pipe and angle of bend.

This set of Fluid Mechanics Problems focuses on “Hydraulic Gradient and Total Energy Line”.

1. Energy gradient line takes into consideration

a) potential and kinetic heads only

b) potential and pressure heads only

c) kinetic and pressure heads only

d) potential, kinetic and pressure heads

Answer: d

Explanation: EGL is obtained by plotting total head at various points along the axis of the pipe.

fluid-mechanics-problems

where H is the total head, P / γ is the pressure head, z is the potential head and v 2 / 2g is the velocity head. Hence, EGL is also called Total Energy Line .

2. Hydraulic gradient line takes into consideration

a) potential and kinetic heads only

b) potential and pressure heads only

c) kinetic and pressure heads only

d) potential, kinetic and pressure heads

Answer: b

Explanation: HGL is obtained by plotting piezometric head at various points along the axis of the pipe.

H p = P ⁄ γ + z

where H p is the piezometric head, P ⁄ γ is the pressure head and z is the potential head.

3. Which of the following is true?

a) EGL always drops in the direction of c

b) EGL always rises in the direction of flow

c) EGL always remains constant in the direction of flow

d) EGL may or may not in the direction of flow

Answer: a

Explanation: EGL is obtained by plotting total head at various points along the axis of the pipe. Since the total head decreases in the direction of flow, EGL will always drop in that direction.

4. Which of the following is true?

a) HGL always drops in the direction of flow

b) HGL always rises in the direction of flow

c) HGL always remains constant in the direction of flow

d) HGL may or may not in the direction of flow

Answer: d

Explanation: HGL is obtained by plotting piezometric head at various points along the axis of the pipe. Since pressure may either rise or fall in the direction of flow, HGL may or may not change in that direction.

5. Which of the following is true?

a) HGL will never be above EGL

b) HGL will never be under EGL

c) HGL will never coincide with EGL

d) HGL will may or may not be above EGL

Answer: a

Explanation: EGL is obtained by plotting total head and HGL is obtained by plotting piezometric head at various points along the axis of the pipe.

fluid-mechanics-problems

H p = P ⁄ γ + z

where H is the total head, P ⁄ γ is the pressure head, z is the potential head, H p is the piezometric head, and v 2 / 2g is the velocity head.

H = Hp + v 2 / 2g Since Hp < H, HGL can never be above EGL.

6. The vertical intercept between EGL and HGL is equal to

a) pressure head

b) potential head

c) kinetic head

d) Piezometric head

Answer: c

Explanation: EGL is obtained by plotting total head and HGL is obtained by plotting piezometric head at various points along the axis of the pipe.

fluid-mechanics-problems

H p = P ⁄ γ + z

where H is the total head, P ⁄ γ is the pressure head, z is the potential head, H p is the piezometric head, and v 2 / 2g is the velocity head.

H – Hp = v 2 / 2g, the vertical intercept between EGL and HGL is equal to the kinetic head.

7. The slope of HGL will be

a) greater than that of EGL for a pipe of uniform cross-section

b) smaller than that of EGL for a pipe of uniform cross-section

c) equal than that of EGL for a pipe of uniform cross-section

d) independent of that of EGL for a pipe of uniform cross-section

Answer: c

Explanation: The vertical intercept between EGL and HGL is equal to the kinetic head. For a pipe of uniform cross-section, there will be no change in the velocity of flow across the pipe. Since the kinetic head remian constant, the slope of HGL will be equal than that of EGL.

8. For a nozzle, the vertical intercept between EGL and HGL

a) increases

b) decreases

c) remains constant

d) may increase or decrease

Answer: a

Explanation: The vertical intercept between EGL and HGL is equal to the kinetic head. For a nozzle, the cross-sectional area decreases in the direction of flow leading to an increase in the velocity of flow across the pipe. Since the kinetic head increases, the vertical intercept between EGL and HGL will increase.

9. For a diffuser, the vertical intercept between EGL and HGL

a) increases

b) decreases

c) remains constant

d) may increase or decrease

Answer: b

Explanation: The vertical intercept between EGL and HGL is equal to the kinetic head. For a diffuser, the cross-sectional area increases in the direction of flow leading to a decrease in the velocity of flow across the pipe. Since the kinetic head decreases, the vertical intercept between EGL and HGL will decrease.

10. Which of the following is true?

a) the slope of EGL will always be greater than that of the axis of the pipe

b) the slope of EGL will always be smaller than that of the axis of the pipe

c) the slope of EGL will always be equal to that of the axis of the pipe

d) the slope of EGL will always be independent of that of the axis of the pipe

Answer: d

Explanation: EGL is obtained by plotting total head at various points along the axis of the pipe.

fluid-mechanics-problems

where H is the total head, P ⁄ γ is the pressure head, z is the potential head, , and v 2 / 2g is the velocity head.

Hence, there is no relation whatsoever between the slope of EGL and that of the axis of the pipe.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Pipes in Series”.

1. The liquid flowing through a series of pipes can take up__________

a) Pipes of different diameters

b) Pipes of the same diameters only.

c) Single pipe only

d) Short pipes only

Answer: a

Explanation: When pipes of different diameters are connected at its ends to form a pipe, this pipe so developed is called as pipes in series. They might not have to be of the same diameters. But, having the same diameters are better as it avoids the losses so developed.

2. What is the total loss developed in a series of pipes?

a) Sum of losses in each pipe only

b) Sum of local losses only

c) Sum of local losses plus the losses in each pipe

d) Zero

Answer: c

Explanation: When the pipes of different diameters are connected in series from end to end to form a pipe line. The total loss so developed is equal to the sum of local losses plus the losses in each pipe. The local losses are developed at the connection point.

3. The total head loss for the system is equal to_________

a) Pipe length

b) Pipe diameter

c) Width of the reservoir

d) Height difference of reservoirs

Answer: d

Explanation: Total head loss for a system is equal to the height difference of the reservoirs. Height difference is denoted by the letter ‘H’. Total head loss can be equated by summing it up with all the local losses and the losses at each pipe.

4. Which among the following is not a loss that is developed in the pipe?

a) Entry

b) Exit

c) Connection between two pipes

d) Liquid velocity

Answer: d

Explanation: Liquid velocity in the pipe is the velocity with which the liquid travels through different cross sections of the pipe. It is a vector field which is used to describe the motion of a continuum. The length of flow velocity vector is equal to the flow speed.

5. Which among the following is the correct formula for head loss?

a) Z 1 -Z 2

b) C

c) T 2 -T 1

d) S 2 -S 1

Answer: a

Explanation: Total head loss for a system is equal to the height difference of the reservoirs. Height difference is denoted by the letter ‘H’. Total head loss can be equated by summing it up with all the local losses and the losses at each pipe. Here, the height difference between the reservoirs is Z 1 -Z 2 .

6. If the two reservoirs are kept at the same level, the head loss is _______

a) Z 1 -Z 2

b) Zero

c) T 2 -T 1

d) S 2 -S 1

Answer: b

Explanation: Total head loss for a system is equal to the height difference of the reservoirs. Height difference is denoted by the letter ‘H’. The height difference between the reservoirs is Z 1 -Z 2 . Since they are of the same level, Z 1 =Z 2 . Therefore, head loss is zero.

7. How do we determine the total discharge through parallel pipes?

a) Add them.

b) Subtract them

c) Multiply them

d) Divide them

Answer: a

Explanation: Total discharge in parallel pipes are determined by adding the discharges so developed in individual pipes. If Q 1 is the discharge through pipe 1 and Q 2 is the discharge through pipe 2. Then the total discharge through parallel pipes is equal to Q 1 +Q 2 .

8. The pipe diameter is ________

a) Directly proportional to fluid density

b) Directly proportional to mass flow rate

c) Inversely proportional to mass flow rate

d) Directly proportional to fluid velocity

Answer: b

Explanation: The pipe diameter is directly proportional to mass flow rate of fluid. Pipe diameter can be calculated if volumetric flow rate and velocity are known. ‘D’ is inversely proportional to its velocity.

9. Define Viscosity.

a) Resistance to flow of object

b) Resistance to flow of air

c) Resistance to flow of fluid

d) Resistance to flow of heat

Answer: c

Explanation: Viscosity is developed due to the relative motion between two surfaces of fluids at different velocities. It happens due to the shear stress developed on the surface of the fluid.

10. Coefficient of friction of a laminar flow is_________

a) R e /16

b) R e /64

c) 16/R e

d) 64/R e

Answer: c

Explanation: Coefficient of friction is defined as the value that shows relationship between force and the normal reaction. It is mainly used to find out an object’s normal force and frictional force. Thus, it is equal to 16/R e .

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Flow through Nozzles”.

1. When a gas is pushed through a pipe, the gaseous molecules are _________ by the pipe’s walls

a) Attracted

b) Absorbed

c) Deflected

d) Dissipated

Answer: c

Explanation: This is because there is no attractive force present in the tube for the process of attraction to occur. Also, the surface of pipes is not an absorbing one, hence absorption is also ruled out. A pipe is not capable of dissipation of the molecules. Hence, the right option is deflected.

2. If the speed of sound is much ________ than that of the gas, the gas density will stay constant.

a) Smaller

b) Larger

c) Equal to

d) Non-existent

Answer: b

Explanation: This is because only with speed of sound Is larger, it’ll be able to compensate for the speed of gas. Under such situations, the gas density will be able to stay constant. If they are equal, density will get compressed.

3. Isentropic nozzle flow states about the movement of a gas or fluid through a narrow orifice without an increase or decrease in ___________

a) Pressure

b) Energy

c) Displacement

d) Entropy

Answer: d

Explanation: Entropy is defined as the measure of degree of randomness. It is a thermodynamics quantity. As this nozzle flow deals with thermodynamics, entropy is the right choice. The other options are not parameters of entropy.

4. In fluid dynamics, the velocity of the fluid in the stagnation point is

a) Zero

b) Infinite

c) Non-existent

d) Negative

Answer: a

Explanation: Stagnant point is a point where there is no movement of the fluid. When there is no movement, the velocity will be 0. Hence the answer is 0.

5. The stagnation state is obtained after a _____________ to zero velocity.

a) Accelerating

b) Decelerating

c) Equilibrium

d) Exponential increase

Answer: b

Explanation: Initially the flow has a velocity. In the stagnant state, the velocity is 0. For this to happen, there should be a deceleration of the velocity. Hence, deceleration is the answer.

6. To refrain from separation in subsonic nozzles, the expansion angle must not be more than _____

a) 10 degrees

b) 20 degrees

c) 30 degrees

d) 40 degrees

Answer: a

Explanation: If the angle is more than 10 degrees, there will be a drift amidst the nozzle. At any angle more than 10 degrees, this separation will occur. But the minimum value is 10 degrees. So, the answer is 10 degrees.

7. Gas flows through the nozzle from an area of _____ pressure  to one of _____ pressure

a) High, low

b) Low, high

c) Same, same

d) Constant, Infinite

Answer: a

Explanation: Anything that flows or runs moves from a region of higher value to lower value. We can take the example of any physical parameter like pressure, altitude etc. Hence, here the gas will flow from high to low pressure regions.

8. Converging-diverging nozzle is also known as __________

a) Pascal nozzle

b) Bernouille’s nozzle

c) Toricelli’s nozzle

d) de Laval’ nozzle

Answer: d

Explanation: This is because this nozzle was invented by Carl de Laval. So, it is also named after him. Hence De-Laval nozzle is the option.

9. When the pressure chamber is big, the flow velocities are _________

a) Large

b) Negligible

c) Constant

d) Increasing

Answer: b

Explanation: When the chamber is large, the area is high. Velocity is inversely proportional to area. So in a large chamber, the flow velocity will be less. It will be negligible.

10. For a compressible, ideal gas, mass flow rate depends on parameters such as flow area, pressure, temperature, properties of the gas, and _________

a) Avogardo’s Number

b) Mach Number

c) Reynold’s Number

d) Le-Grange’ Number

Answer: b

Explanation: Mass flow rate should depend on the velocity. Here Mach number denotes the velocity. So, the Mach number gives the right answer.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Water Hammer in Pipes”.

1. Where is a water hammer developed?

a) Reservoir

b) Penstock

c) Turbine blades

d) Pipe line

Answer: b

Explanation: Water hammer is developed in a penstock. It is developed due to the reduction in load on the generator. This reduction causes the governor to close the turbine gates and thus creating an increased pressure in the penstock.

2. Which among the following is true for hydroelectric power plants?

a) Operating cost is low and initial cost is high

b) Both operating and initial cost are high

c) Both operating and initial cost are low

d) Operating cost is high and initial cost is low

: a

Explanation: For a hydroelectric power plant, the operating cost is low and the initial cost is high. The initial cost is high due to the large area required for construction. Since, the fuel cost is comparatively cheaper, the operating cost is low.

3. The power output of the turbine in a hydroelectric plant depends on______________

a) Type of dam and its system efficiency

b) Discharge and system efficiency

c) Type of turbine and type of dam

d) Type of turbine and area of the reservoir

Answer: b

Explanation: The power output of the turbine in a hydroelectric plant depends on the system efficiency and discharge. In a hydroelectric power plant, the discharge and head are directly proportional to its system efficiency.

4. Water hammer is developed in which power plant?

a) Solar

b) Nuclear

c) Hydro

d) Wind

Answer: c

Explanation: Water hammer is defined as a pressure surge or wave caused in a pipeline. This happens due to the forceful stop of the fluid in motion. It happens mainly when the valve closes suddenly in a pipeline system. Thus, option Hydro is the right choice.

5. Which among the following are commercial sources of energy?

a) Solar energy

b) Animal wastes

c) Agricultural wastes

d) Wood

Answer: a

Explanation: Solar energy is a commercial source of energy among the following options. All energy sources that serve a commercial purpose are called as commercial sources of energy. Some good examples are Solar, tidal, wind, geothermal, wave etc.

6. Which is the most suitable place to build a hydroelectric power plant?

a) Deserts

b) Grasslands

c) Hilly areas

d) Underground

Answer: c

Explanation: Hilly areas are the most preferred areas to build a hydroelectric power plant. Hilly areas are preferred because dams play an important role. Building of dams in hilly areas is easier because large reservation can be obtained.

7. In a hydroelectric power plant, where is the penstock used?

a) Between dam and the turbine

b) Between turbine and discharge drain

c) Turbine and heat exchanger

d) Heat exchanger and fluid pump

Answer: a

Explanation: Hydroelectric powerplants play an important role in energy conversion, to produce electricity. It is a commercial method. Penstock is closed conduit. It is connected in between the dam and the turbine in the hydro station.

8. Which among the following is used as a regulating reservoir?

a) Reservoir

b) Spillways

c) Forebay

d) Penstock

Answer: c

Explanation: Forebay serves as a regulating reservoir. It stores water on a temporary basis, during light load period. It has got an enlarged body of water situated above the intake. This intake pipe is used to store water on a temporary basis.

9. Gross head is defined as______

a) Difference of flow of object

b) Difference of flow of air

c) Difference of flow of water

d) Difference of water level between the head race and tail race

Answer: d

Explanation: Gross head is defined as the difference of water level between the head race  and the tail race. Gross head can be denoted as . It plays an important role in determining the power losses in the pipeline.

10. What is the function of a surge tank?

a) It causes water hammer

b) Produces surge in the pipeline

c) Relieves water hammer

d) Supplies water at constant pressure

Answer: c

Explanation: The main purpose of a surge tank is to relieve water hammer pressure in the penstock. It absorbs the changes in the water requirements. After absorbing the water changes, it reduces the water hammer and the negative pressure developed in the pressure stock.

11. Hydro-graph is a graph that shows________

a) Load curve

b) Energy curve

c) Mass curve

d) Volume curve

Answer: a

Explanation: Hydrograph is a graph that indicates the power available at different streams of water. It helps us determine the load curve. This load curve is used to determine the electrical power so developed in the hydroelectric power plant.

12. What is the function of a pump storage scheme?

a) Improve power factor

b) Improve mass factor

c) Improve plant capacity factor

d) Improve volume factor

Answer: c

Explanation: In a hydroelectric power plant, the main function of pump storage scheme is to make more water available during any deficiency. It strengthens the economic factor of the hydroelectric power plant.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Pipe Network”.

1. What is the aim of pipe network analysis?

a) To determine the mass of fluid

b) To determine the volume of fluid

c) To determine the flow rates and pressure drops

d) To determine the cross sections of the pipe

Answer: c

Explanation: Pipe analysis is an analysis that is carried out in various aspects. It mainly concentrates on the fluid through a hydraulics network. Hydraulic networks are networks that contain several interconnected branches. The aim is to determine pressure drops and fluid flow rates.

2. The steady- state flow must satisfy ___________

a) Kirchhoff’s law

b) Newtons law

c) Rutherford’s experiment

d) Kepler’s law

Answer: a

Explanation: The steady state flow must satisfy Kirchhoff’s first and second law. First law states that the total flow into the junction equals the total flow away from the junction. Second law is called the law of conservation of mass. It states that between two junctions, the head loss is independent of the path followed.

3. What are the assumptions made for a fluid flow through a pipe?

a) Fluid inertia is not taken

b) Viscosity is not taken

c) Volume is not considered

d) Mass is not considered

Answer: a

Explanation: During a fluid flow through a pipe, there are various design considerations. But, the two major assumptions are that the flow is assumed to be fully developed. Also, fluid inertia is not taken into account.

4. Which among the following is not global parameters of fluid?

a) Viscosity

b) External diameter

c) Density

d) Mass flow rate

Answer: b

Explanation: External diameter is not a global parameter. It is one of the most essential pipelining parameters. It helps in determining the type of pipe and material to be used for the same.

5. What is the default value of pipe length?

a) 5 meters

b) 20 meters

c) 10 meters

d) 30 meters

Answer: a

Explanation: Pipe analysis is carried out in various aspects. It mainly concentrates on the fluid through a hydraulics network. After the analysis, they have determined the default length of the pipe as 5 meters.

6. What is the best suitable type of pipe?

a) Hard

b) Rigid

c) Tough

d) Malleable

Answer: b

Explanation: The best suitable parameter to determine the pipe is either rigidity or flexibility. If we set it with rigidity, the compliance of the walls are not taken into account. Flexibility is preferred for metal pipes and hoses.

7. What is the default value of specific heat ratio in pipelines?

a) 1

b) 1.2

c) 1.4

d) 2

Answer: c

Explanation: Pipe analysis is carried out in various aspects. It mainly concentrates on the fluid through a hydraulics network. Specific heat ratio is the ratio of heat to the constant volume chamber block. It has got a default value of 1.4.

8. Where is the surge tank located in a hydroelectric power plant?

a) Dam

b) Head race

c) Tail race

d) Turbine

Answer: d

Explanation: In a hydroelectric power plant, the surge tank is located close to the power station. It is mainly close to the ground to reduce the light. The surge tank in medium and high head turbines are located at the inlet of the turbine.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Ideal Indicator Diagram”.

1. Which among the following can be assessed based on the indicator diagram?

a) Overall performance of engine

b) Area of the reservoir

c) Load the engine can take

d) Speed of the Engine

Answer: a

Explanation: The main purpose of the indicator diagram is to asses the overall performance of the engine. It is done by assessing the performance of each unit of the main engine. It plays an important role in the manufacture of ship engine.

2. How are the indicator diagrams drawn for the ship?

a) By providing the ship’s mass

b) By providing the ship’s volume

c) By matching ships sea trial diagrams

d) By differentiating the diagrams

Answer: c

Explanation: Indicator diagrams are drawn by taking the diagrams at regular intervals. This time taken at regular interval is matched with the ship’s sea trial diagrams. The comparison is to check if there is any significant difference in the performance.

3. Which among the following is not a type of indicator diagram?

a) Power card

b) Draw card

c) Compression diagram

d) Power house

Answer: d

Explanation: Power house is not a type of indicator diagram. It is also called as the power station. The main purpose of the power house is to supply electrical power to any system for an efficient working of the system.

4. Which among the following cannot be determined by indicator diagram?

a) The actual power generated

b) Cogeneration

c) Compression inside the cylinder

d) Exhausting and scavenging process

Answer: b

Explanation: Heat generated from clean heat and power is called as cogeneration. Cogeneration can be defined as combined heat and power that used to heat engine or the power station to generate electricity. Therefore, cogeneration cannot be determined by an indicator diagram.

5. High loading in engines will lead to_________

a) Speed rise

b) Temperature rise

c) Bearing damage

d) Volume expansion

Answer: c

Explanation: High loading in engines will lead to bearing damage. It also leads to several other problems like cracking, breaking etc. So, it is very important in assessing and reading these diagrams correctly.

6. What type of indicator device is used nowadays?

a) Digital pressure indicator

b) Mechanical indicator

c) Electrical indicator

d) Ionization Gauge

Answer: a

Explanation: In earlier days, the indicator diagram was assessed with the help of mechanical indicator. But now, we use a digital pressure indicator. It has got a lot of advantages over the mechanical one. It has a compact hand-held unit with a computer display system.

7. How can we asses the indicator diagram by looking at the card diagram?

a) Comparing the maximum firing pressure and compression pressure

b) Dead weight method

c) Conveyor method

d) Ionization method

Answer: a

Explanation: Using a card diagram, we can asses the indicator diagram. This process is performed using multiple parameters. One of them is the maximum firing pressure and the other is the comparison pressure.

8. Which among the following is not an effect of deficiency in the indicator diagram?

a) Bad quality of fuel

b) Fuel pump leakage

c) Low fuel pressure

d) Fuel temperature rise

Answer: d

Explanation: Deficiencies in an indicator diagram are classified into many types. Deficiencies can be determined using the card diagram. Card diagram contains maximum firing pressure and compression pressure which does not depend on the temperature rise of fluid.

9. Deficiency type 3 is not caused due to_________

a) Leaking exhaust valve

b) Resistance to flow of air

c) Low scavenging pressure

d) High linear wear

Answer: b

Explanation: Deficiencies in an indicator diagram are classified into many types. Deficiencies can be determined using the card diagram. Card diagram contains maximum firing pressure and compression pressure. In deficiency 3, the compression pressure is low and peak pressure is also low.

10. Deficiency type 4 is caused due to_________

a) Resistance to flow of air

b) Leaking exhaust valve

c) Low scavenging pressure

d) Overload of engine

Answer: d

Explanation Deficiencies in an indicator diagram are classified into many types. Deficiencies can be determined using the card diagram. Card diagram contains maximum firing pressure and compression pressure. In deficiency 4, compression pressure is high and peak pressure is also high leading to the overload of an engine.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Effect of Acceleration in Suction and Delivery Pipes on Indicator Diagrams”.

1. What is the full form of NPSH?

a) Net pipe suction head

b) Net positive suction head

c) Non-positive suction head

d) Non-polar suction head

Answer: b

Explanation: The full form of NPSH is net positive suction head. It is defined as the margin of pressure over vapour pressure. It happens at the pump suction nozzle.

2. What is the formula for NPSH?

a) P s -P vap

b) V s -V vap

c) T s -T vap

d) M s -M vap

Answer: a

Explanation: NPSH is defined as the margin of pressure over vapour pressure. It happens at the pump suction nozzle. It is the difference between the suction pressure and vapour pressure. Thus, the correct option is P s -P vap .

3. What is absolute pressure?

a) Momentum pressure to thermal pressure

b) Thermal pressure to momentum pressure

c) Atmospheric pressure plus gauge pressure

d) Atmospheric pressure by gauge pressure

Answer: c

Explanation: Absolute pressure is defined as the summation of Atmospheric pressure plus gauge pressure. This equation provides the answer in units of pressure. The obtained psi can be converted to units of head.

4. What is the unit of NPSH?

a) kPa

b) kgm

c) kg/m

d) kg

Answer: a

Explanation: Unit of NPSH can be expressed as units of specific energies. All the units in NPSH are psi units. The psi units are kilopascal, bar, pounds per square inch etc. So, kPa is the correct option.

5. What does ‘g’ in psig mean?

a) Pressure is measured below absolute pressure

b) Pressure is measured above absolute pressure

c) Pressure is measured below absolute zero

d) Pressure is measured above absolute zero

Answer: b

Explanation: All the units in NPSH are psi units. The psi units are kilopascal, bar, pounds per square inch etc. The ‘g’ in psig indicates that the pressure is measured above the absolute pressure.

6. What does ‘a’ in psia mean?

a) Pressure is measured below absolute pressure

b) Pressure is measured above absolute pressure

c) Pressure is measured below absolute zero

d) Pressure is measured above absolute zero

Answer: d

Explanation: All the units in NPSH are psi units. The psi units are kilopascal, bar, pounds per square inch etc. The ‘a’ in psia indicates that the pressure is measured above absolute zero which is a perfect vacuum.

7. Which among the following happens at the first half of NPSH?

a) Vapour pressure

b) Atmospheric pressure

c) Suction pressure

d) Discharge pressure

Answer: c

Explanation: During the first half of the NPSH, the suction of air takes place. For the suction of an air, a strong suction pressure is required. Sometimes, the elevation of gauge must also be added. But, most of the times it is considered negligible.

8. Which among the following happens in the second half of NPSH?

a) Vapour pressure

b) Atmospheric pressure

c) Suction pressure

d) Discharge pressure

Answer: a

Explanation: During the second half of the NPSH, vapour pressure is more difficult to determine. It is a measure of the desire of liquids. Cool water has a low vapour pressure. Thus, the option is Vapour pressure.

9. Vapour pressure depends on_______

a) Pressure

b) Temperature

c) Density

d) Viscosity

Answer: b

Explanation: Vapour pressure depends on temperature only. With the increase in temperature, the vapour pressure increases. It increases until it reaches the critical temperature. At the critical temperature, the vapour pressure tends to slowly vanish.

10. Which among the following is not a type of pipe?

a) Stainless steel pipes

b) PVC piping

c) Brass pipes

d) Wooden pipes

Answer: d

Explanation: Wooden pipes for transportation and other important facilities is not feasible. Wood has various properties against water. Water flowing through the wooden pipe will slowly reduce the strength of the wood which may lead to cracks.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Maximum Speed of a Reciprocating Pump”.

1. A reciprocating pump is a class of _________

a) Negative displacement

b) Positive displacement

c) Zero displacement

d) Infinite displacement

Answer: b

Explanation: A reciprocating pump consists of a piston pump, plunger and diaphragm pump. It is a class of positive displacement. Reciprocating pumps will last for years and decades.

2. The simplest application of the reciprocating pump is___________

a) Piston pump

b) Plunger

c) Diaphragm pump

d) Bicycle pump

Answer: d

Explanation: Bicycle is the pump is the simplest application of the reciprocating pump. It works on the principle of simple hand operated reciprocating pump. It is used to inflate bicycle tires and various sporting balls.

3. Power operated deep well reciprocating pump is divided into__________

a) Single and double acting

b) Single and multi-stage

c) Piston and plunger

d) Conductive and nonconductive

Answer: a

Explanation: Power operated deep well reciprocating pump is divided into single and double acting. It is classified on the basis of its mechanism. It is distinguished depending on the function of the piston.

4. Which among the following is not an example of a reciprocating pump?

a) Hand pump

b) Wind mill

c) Axial piston pump

d) Turbine blades

Answer: d

Explanation: A reciprocating pump is a class of a positive displacement pump. It includes a piston pump, plunger and a diaphragm pump. It has a long life. Turbine blades are not an example of the reciprocating pump.

5. Pump converts mechanical energy into ________

a) Pressure energy only

b) Kinetic energy only

c) Pressure and kinetic energy

d) Potential energy

Answer: c

Explanation: The main function of the pump is to transfer and convert mechanical energy of a motor into pressure energy and kinetic energy. It plays an important role in the transfer of fluid across the pipeline.

6. Which among the following is not a positive displacement pump?

a) Centrifugal

b) Reciprocating

c) Rotary

d) Ionization pump

Answer: a

Explanation: Centrifugal pumps are not a positive displacement pump. They are a subclass dynamic work absorbing turbo machinery. They are used to transport fluids. It transports fluid by conversion of rotational kinetic energy to hydrodynamic kinetic energy.

7. How do we measure the flow rate of liquid?

a) Coriolis method

b) Dead weight method

c) Conveyor method

d) Ionization method

Answer: a

Explanation: Coriolis concept of measurement of fluid takes place through the rotation with the reference frame. It is an application of the Newton’s Law. The device continuously records, regulates and feeds large volume of bulk materials.

8. Which among the following is called as the velocity pump?

a) Centrifugal

b) Reciprocating

c) Rotary

d) Ionization pump

Answer: a

Explanation: Centrifugal pumps are not a positive displacement pump. They are a subclass dynamic work absorbing turbo machinery. They are used to transport fluids. It transports fluid by conversion of rotational kinetic energy to hydrodynamic kinetic energy.

9. Discharge capacity of a reciprocating pump is lower than that of reciprocating pump.

a) True

b) False

Answer: True

Explanation: Discharge capacity of the reciprocating pump is lower than that of the reciprocating pump. Discharge capacity of fluids is defined as the discharge in terms of the volumetric flow rate. It helps to regulate the flow through a cross sectional area.

10. Which among the following is a high-pressure pump?

a) Centrifugal

b) Reciprocating

c) Rotary

d) Ionization pump

Answer: b

Explanation: Reciprocating pump is the most suitable high-pressure pumps at moderate or low discharges. A reciprocating pump is a class of a positive displacement pump. It includes a piston pump, plunger and a diaphragm pump.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Dimensional Homogenity”.

1. Which among the following is not a fundamental dimension?

a) [L]

b) [M]

c) [T]

d) [kg]

Answer: d

Explanation: It is essential to adopt a consistent dimensional quantity. Thus, we adopt a basic form to categorize dimension quantities. For this purpose, we adopt a comparison of the quantities in SI or MKS units.

2. The fundamental dimensional quantities are related by________

a) Avagadaro’s law

b) Newton’s second law

c) Newtons first law

d) Newton’s third law

Answer: b

Explanation: Newton’s 2 nd law is the most suitable one for determining the dimensional quantities. We know that, F=ma. Where F = Force , m = mass in kg, and a= acceleration in m/s 2 .

3. Force can be written as______

a) [M][L][T] -2

b) [M][L][T] 2

c) [M][L][T]

d) [M][L][T] 3

Answer: a

Explanation: Force can be written dimensionally by [F]= [M][L][T] -2 . This is by adopting the basic SI or MKS units. Where, [M] is the mass, [L] is the length and [T] is the time. Thus, the correct option is [M][L][T] -2 .

4. How can we write power using the MLT system?

a) [M][L][T] -2

b) [M][L] 2 [T] 3

c) [M][L][T]

d) [M][L][T] 3

Answer: b

Explanation: Power can be written dimensionally by [M][L]2[T] 3 . This is by adopting the basic SI or MKS units. Where, [M] is the mass, [L] is the length and [T] is the time. Thus, the correct option is [M][L] 2 [T] 3 .

5. How can we write dynamic viscosity using the MLT system?

a) [M][L][T] -2

b) [M][L] 2 [T] 3

c) [M][L] -1 [T] -1

d) [M][L][T] 3

Answer: c

Explanation: Dynamic viscosity can be written dimensionally by [M][L]-1[T] -1 . This is by adopting the basic SI or MKS units. Where, [M] is the mass, [L] is the length and [T] is the time. Thus, the correct option is [M][L] -1 [T] -1 .

6. How can we write kinematic viscosity using the MLT system?

a) [M][L][T] -2

b) [M] 0 [L] 2 [T] -1

c) [M][L] -1 [T] -1

d) [M][L][T] 3

Answer: b

Explanation: Kinematic viscosity can be written dimensionally by [M]0[L]2[T] -1 . This is by adopting the basic SI or MKS units. Where, [M] is the mass, [L] is the length and [T] is the time. Thus, the correct option is [M] 0 [L] 2 [T] -1 .

7. How can we write momentum using the MLT system?

a) [M][L][T] -2

b) [M] 0 [L] 2 [T] -1

c) [M][L][T] -1

d) [M][L][T] 3

Answer: c

Explanation: Momentum can be written dimensionally by [M][L][T] -1 . This is by adopting the basic SI or MKS units. Where, [M] is the mass, [L] is the length and [T] is the time. Thus, the correct option is [M][L][T] -1 .

8. How can we write specific weight using the FLT system?

a) [F]

b) [F][T]

c) [F][L][T]

d) [L]

Answer: a

Explanation: Specific can be written dimensionally by [F]. This is by adopting the basic SI or MKS units . Where, [F] is the mass, [L] is the length and [T] is the time. Thus, the correct option is [F].

9. How can we write specific mass using the MLT system?

a) [M][L][T] -2

b) [M] 0 [L] 2 [T] -1

c) [M][L] -3 [T] 0

d) [M][L][T] 3

Answer: c

Explanation: Specific mass can be written dimensionally by [M][L]-3[T] 0 . This is by adopting the basic SI or MKS units. Where, [M] is the mass, [L] is the length and [T] is the time. Thus, the correct option is [M][L] -3 [T] 0 .

10. How can we write energy using the MLT system?

a) [M][L] 2 [T] 2

b) [M] 0 [L] 2 [T] -1

c) [M][L] -3 [T] 0

d) [M][L][T] 3

Answer: a

Explanation: Energy or work can be written dimensionally by [M][L]2[T] 2 . This is by adopting the basic SI or MKS units. Where, [M] is the mass, [L] is the length and [T] is the time. Thus, the correct option is [M][L] 2 [T] 2 .

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Rayleighs Method”.

1. What is the mathematical technique used to predict physical parameters?

a) Combustion analysis

b) Pressure analysis

c) Dimensional analysis

d) Temperature analysis

Answer: c

Explanation: Dimensional analysis is a process which is used to determine physical parameters that influence the fluid flow. The analysis is based on the fundamental units. The fundamental units are mass, length and time.

2. Which among the following method is used to find a functional relationship with respect to a parameter?

a) Rayleigh’s method

b) Rutherford’s method

c) Newton’s laws

d) Doppler effect

Answer: a

Explanation: Rayleigh’s method is a basic method for finding the functional relationship. The functional relationship is found with respect to a physical parameter. It is illustrated using the MLT system.

3. Which among the following is not the correct symbol?

a) Size- l

b) Velocity – v

c) Gravity – g

d) Viscosity – a

Answer: d

Explanation: The symbol used for viscosity is false. Viscosity is denoted by the symbol ‘µ’ . It is defined as the resistance to flow of fluid. Resistance takes place as one layer of fluid slides over the other.

4. Which among the following is the correct format for Rayleigh’s method?

a) D = f

b) D = 

c) D = f

d) D = f

Answer: a

Explanation: The correct format for Rayleigh’s method is D = f. Where, D is the dimensional analysis, ‘f’ is the function, and the variables inside the bracket are the physical parameters to determine the function.

5. What does ‘C’ denote in D = Cl a ρ b μ c V d g e ?

a) Function

b) Dimensions

c) Dimensionless constant

d) Number of parameters

Answer: c

Explanation: ‘C’ in D = Cl a ρ b μ c V d g e denotes dimensionless constant and a,b,c,d,e, are its exponents. This is the fundamental purpose of Rayleigh’s method.

6. Why does Rayleigh’s method have limitations?

a) To many variables

b) Format

c) Exponents in between variables

d) Many exponents

Answer: c

Explanation: The main limitation of the Rayleigh’s method is that it has exponential relationship between the variables. It makes it more complex for solving. Since, more variables with exponents will lead to a confusion in the solving process.

7. Which among the following is same as the Rayleigh’s method?

a) Buckingham method

b) Dead weight method

c) Conveyor method

d) Ionization method

Answer: a

Explanation: Buckingham method is also called as the ‘pi’ theorem method. This method can be illustrated by various moving components. It plays an important role in finding the drag of various moving objects.

8. Which among the following is not a dimensionless number?

a) Reynolds

b) Froude

c) Mach

d) Cartesian

Answer: d

Explanation: Dimensionless numbers are numbers with a dimension of one. It is a pure number. It does not contain any physical unit. No change takes place due to altering of any variable.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Model Analysis”.

1. What is a model analysis?

a) A small-scale replica

b) Actual structure

c) Theory structure.

d) Adopted structure

Answer: a

Explanation: Model analysis is defined as a small-scale replica of the actual structure. Model analysis need not be smaller all the time. They can even be larger than the prototype.

2. What is a prototype?

a) A small-scale replica

b) Actual structure

c) Theory structure.

d) Adopted structure

Answer: b

Explanation: Prototype is the actual structure that needs to be constructed. For a better understanding of the model, we prepare a model analysis. They can even be larger than the prototype.

3. Advantage of a model analysis is_________

a) Performance cannot be predicted

b) The relationships between the variable cannot be obtained

c) Shear stress to thermal diffusivity

d) Alternative designs can be predicted

Answer: d

Explanation: One of the major advantages of the model analysis is that we can predict the alternative designs. It can also predict the performance of the machine in advance.

4. Why do we need a model analysis?

a) For determining the dimensions

b) To provide a safe design

c) To check the shear stress

d) To check the thermal diffusivity

Answer: b

Explanation: One of the major advantages of the model analysis is that we can predict the alternative designs. It provides the safest design in the most economical way.

5. The similarity between the motion of model and prototype is_________

a) Dynamic similarity

b) Potential similarity

c) Kinematic similarity

d) Design similarity

Answer: c

Explanation: Kinematic similarity is defined as the similarity between motion of the model and the prototype. It exists in between the model and prototype. The points in the model and prototype are of the same magnitude.

6. The similarity between the forces of model and prototype is ________

a) Dynamic similarity

b) Potential similarity

c) Kinematic similarity

d) Design similarity

Answer: a

Explanation: Dynamic similarity is defined as the similarity between forces of a model and the prototype. It exists in between the model and prototype. The points in the model and prototype are of the same magnitude.

7. Which among these forces does not act in a moving fluid?

a) Inertial force

b) Viscous force

c) Gravity force

d) Drag

Answer: d

Explanation: Drag does not take place in moving fluids. Moving fluids are restricted by a viscous force and move along an inertial force. The gravitational force tends to act perpendicular to the fluid surface.

8. What is the formula for elastic force?

a) Elastic stress/area

b) Elastic strain/area

c) Elastic stress*area

d) Elastics stress* Elastic strain

Answer: c

Explanation: Elastic force is a force that is developed by a material to retain to its original position. It regains its shape after a period of time. When an elastic material is compressed or stretched, it develops an elastic force.

9. For a dynamic similarity between a model and a prototype, the ratio of their forces in the model and the prototype must be equal.

a) True

b) False

Answer: a

Explanation: For a dynamic similarity between a model and a prototype, the ratio of their forces in the model and the prototype must be equal. It means that the dynamic similarity between a model and a prototype must be the same.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Similitude – Types of Similarities”.

1. Similitude is a concept applicable to the testing of _________

a) Mathematical models

b) Physical models

c) Engineering models

d) Chemical models

Answer: c

Explanation: Similitude is an essential concept that is applicable to the testing of basic engineering models. A model has a similitude with a real-time application. It shares the same geometry. Similarity and similitude are interchangeable at times.

2. Which among the following is the main application for Similitude?

a) Ships

b) Cars

c) Hydraulics

d) Train

Answer: c

Explanation: Similitude plays an important role in various applications. One of the major applications are hydraulics and aerospace engineering. Its main purpose is to test the fluid flow at different conditions of scaled model.

3. Which among the following is not a criteria to achieve similitude?

a) Geometric similarity

b) Kinematic similarity

c) Dynamic similarity

d) Conditional similarity

Answer: d

Explanation: The criteria required to achieve similitude are geometric similarity, kinematic similarity and dynamic similarity. All these similarities play a major role in regard with the real-time applications. Similarity and similitude are interchangeable at times.

4. A model of with same shape is__________

a) Geometric similarity

b) Kinematic similarity

c) Dynamic similarity

d) Conditional similarity

Answer: a

Explanation: Geometric similarity is a similarity that follows a real-time application. It is model that has the same shape for any sort of application. It is measured in scaled quantities.

5. Which among the following have similar fluid streamlines?

a) Geometric similarity

b) Kinematic similarity

c) Dynamic similarity

d) Conditional similarity

Answer: b

Explanation: In kinematic similarity, fluid flow of model and real-time application takes place. Here, the model and the real application must undergo similar time rates in motion changes. Thus, it has similar fluid streamlines.

6. Which among the following have the same forces acting on them?

a) Geometric similarity

b) Kinematic similarity

c) Dynamic similarity

d) Conditional similarity

Answer: c

Explanation: Dynamic similarities have the same forces acting on them. That means, the ratios of all the forces acting on the fluid particles are constant. Also, the ratio of the forces acting on the boundary surfaces are also a constant.

7. All the parameters in a similitude are described using_________

a) Continuum mechanics

b) Solid mechanics

c) Diesel mechanics

d) Aircraft mechanics

Answer: a

Explanation: A branch of mechanics that deals with the analysis of mechanical behaviour of materials and kinematics of materials. They are used for modelling purposes. It is modelled in continuous mass.

8. Physical similitude has exactly the same geometric shape of the prototype.

a) True

b) False

Answer: a

Explanation: Physical similitude is also called the similitude of shape. It is for modelling the same geometric shape as that of its prototype. Which means, that the shape will have to be divided by a scale factor.

9. Which among the following is a standard scale for a similitude?

a) 1:250

b) 1:50

c) 1:25

d) 1:100

Answer: c

Explanation: To design a similitude with a specific dimension, we must fix a scale. The standard system has fixed the scale as 1:25. This was fixed for an uniformity in dimensions.

10. In similitude, F application =F model *3.44

a) True

b) False

Answer: a

Explanation: A model test was conducted to determine this relation. The force and velocity that were measured in the model are to be scaled. This helps to find the force that can be expected for a real-time application.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Types of Forces Acting in Moving Fluid”.

1. Which among the following force is developed due to resistance of a fluid flow?

a) Viscous force

b) Inertial force

c) Gravity force

d) Pressure force

Answer: a

Explanation: Viscous force is the force that is developed due to resistance of a fluid flow. Viscous force is equal to the product of shear stress due to viscosity and surface area of the fluid. It acts in the opposite direction to that of the acceleration.

2. Which among the following force is developed due to resistance in its state of motion?

a) Viscous force

b) Inertial force

c) Gravity force

d) Pressure force

Answer: b

Explanation: Inertial force is the force that has resistance to any physical object that undergoes a change in its state of motion. Inertial force is the product acceleration of fluid and its mass. It acts opposite to the direction of acceleration.

3. Which among the following is the correct formula for gravitational force?

a) F= Gm 1 m 2 /r 2

b) F= Gm 1 m 2

c) F= m 1 m 2 /r 2

d) F= Gm 1 m 2 /r 3

Answer: a

Explanation: Gravitational force was derived by Newton’s theory of gravitation. It is defined as the product of mass and acceleration due to gravity of the fluid flow. It is mainly present in cases of open surface fluid flow.

4. Which among the following is present in pipe flow?

a) Viscous force

b) Inertial force

c) Gravity force

d) Pressure force

Answer: d

Explanation: Pressure is a force that is applied perpendicular to the surface of an object over a unit area of force. It is defined as the product of pressure intensity and cross-sectional area of the flowing fluid. Pressure force is present in case of pipe flow.

5. A force that is caused due to attraction of particles in the layer of fluid bulk is called?

a) Viscous force

b) Inertial force

c) Surface tension force

d) Pressure force

Answer: c

Explanation: Surface tension is caused due to the attraction of particles in the surface layer of the fluid in bulk quantities. Surface tension force is defined as the product of surface tension and length of flowing fluid.

6. A force that is needed to bring back the body to its original position is called as?

a) Viscous force

b) Elastic force

c) Gravity force

d) Pressure force

Answer: c

Explanation: Elastic force is the force that brings a body back to its original position. It is defined as the product of elastic stress and the area of the flowing fluid.

7. How do we measure the flow rate of liquid?

a) Coriolis method

b) Dead weight method

c) Conveyor method

d) Ionization method

Answer: a

Explanation: Coriolis concept of measurement of fluid takes place through the rotation with the reference frame. It is an application of the Newton’s Law. The device continuously records, regulates and feeds large volume of bulk materials.

8. The three major fluid forces are Buoyancy, drag and lift.

a) True

b) False

Answer: a

Explanation: Buoyancy, drag and lift are the three major fluid forces. These forces have significant importance in various applications. For example: Shotput, badminton, cricket, baseball, cycling, swimming etc.

9. The drag force acts in _____ to the flow velocity.

a) Perpendicular direction

b) Same direction

c) Opposite direction

d) Different directions

Answer: c

Explanation: The drag force acts in the opposite direction to that of the relative flow velocity. It acts in the opposite direction with respect to a surrounding fluid flow. Thus, option Opposite direction is correct.

10. Drag force is affected by__________

a) Cross sectional area and smoothness

b) Rigidity and density

c) Pressure and temperature

d) Mass

Answer: a

Explanation: Drag force is affected by cross sectional area and smoothness. If it is affected by cross sectional area, then it is called form drag. If it is affected by surface smoothness, then it is called as surface drag.

11. The lift force acts in _____ to the flow velocity.

a) Perpendicular direction

b) Same direction

c) Opposite direction

d) Different directions

Answer: a

Explanation: The lift force acts in the perpendicular direction to that of the relative flow velocity. It acts in the perpendicular direction with respect to a surrounding fluid flow. Thus, option Perpendicular direction is correct.

12. Which among the following is the correct formula for drag?

a) D = Cd * A * 0.5 * r * V 2

b) D = Cd * A * 0.5 * r * V*2

c) D = Cd * A * 0.5 * r * V/2

d) D = 0.5 * r * V

Answer: a

Explanation: The drag force acts in the opposite direction to that of the relative flow velocity. It acts in the opposite direction with respect to a surrounding fluid flow. Thus, the correct option is D = Cd * A * 0.5 * r * V 2 .

13. Which among the following is the correct formula for lift?

a) D = Cl * A * 0.5 * r * V 2

b) D = Cl * A * 0.5 * r * V*2

c) D = Cl * A * 0.5 * r * V/2

d) D = 0.5 * r * V

Answer: a

Explanation: The lift force is a force that acts in the perpendicular direction to that of the relative flow velocity. It acts in the perpendicular direction with respect to a surrounding fluid flow. Thus, the correct option is D = Cl * A * 0.5 * r * V 2 .

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Model Testing of Partially Submerged Bodies”.

1. What is model testing?

a) Performance testing

b) Partial testing

c) Function testing

d) Overall testing

Answer: a

Explanation: The process in fluid mechanics that is used to study the complex fluid dynamics is called as model testing. It is a performance testing. It helps to test models after a standard scaling. Models are usually smaller than the final design.

2. The performance test is completed after completion of________

a) Casing inspection

b) Regulation

c) Pump enhancement

d) Hydrostatic check

Answer: a

Explanation: The pump casting test starts with the inspection of material. It is a Non-destructive testing method. It is completed after completion of casting inspection. It depends on the pump design.

3. Which test is performed after the pump inspection?

a) Casing inspection

b) Casing hydrostatic test

c) NPSH test

d) Mechanical running test

Answer: b

Explanation: After the inspection, the pump casing hydrostatic test is performed. It takes place only after successful completion of the pump casing inspection.

4. The pump hydrostatic test is tested at __________

a) 2 times the maximum allowable work pressure

b) 3 times the maximum allowable work pressure

c) 5 times the maximum allowable work pressure

d) 1.5 times the maximum allowable work pressure

Answer: d

Explanation: The pump hydrostatic test is tested at 1.5 times the maximum allowable work pressure. It can be found out on the pump datasheet. The pump inspector does not require the calculation of pressure test.

5. What does SME stand for?

a) Subject mass export

b) Subject mass expert

c) Subject matter expert

d) Subject matter export

Answer: c

Explanation: SME stands for Subject Matter Expert. After the inspector has made an inspection on the finished material. It is further sent to the SME. The main function of the SME is to approve the finished material.

6. What does NPSH stand for?

a) Net positive suction head

b) Net positive super head

c) Net planar suction head

d) Non-planar suction head

Answer: a

Explanation: NPSH stands for Net Positive Suction Head. The main function of the NPSH test is to measure the ability of the pump. It helps to avoid cavitation at the inlet section of the pump.

7. How long is the pump mechanical run test performed?

a) 1 hour

b) 2 hours

c) 3 hours

d) 4 hours

Answer: d

Explanation: Pump Mechanical run test is performed for nearly 4 hours. Its main function is to prove that pump works under stable condition. It also helps to determine if all the variables are within the acceptance range.

8. Which among the following is not a pump operating parameter?

a) Power consumption

b) Bearing temperature

c) Density

d) Shaft speed

Answer: c

Explanation: Every parameter plays an important role in determining the pump operation. Density is not a parameter on pump mechanical run test. Each parameter operate for nearly 10 to 15 minutes.

9. A test that is performed at different flow rates is__________

a) Casing inspection

b) Casing hydrostatic test

c) NPSH test

d) Vibration test

Answer: d

Explanation: Pump vibration testing is performed during the performance test at different flow rates. It also takes place during the mechanical running test at a rated flow rate.

10. What does FFT in vibration testing stand for?

a) Fast Fourier Transformation

b) Fast Foil Temperature

c) Fast Foil Transformation

d) Feature Fourier Transformation

Answer: a

Explanation: FFT stands for Fast Fourier Transformation. Depending on the pump design, housing and vibration it is measured and plotted. FFT is a spectrum which denotes each data point from minimum to maximum.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Dimensionless Numbers”.

1. The rate at which the particles of fluid can spread is called_______

a) Surface tension

b) Diffusivity

c) Viscosity

d) Kinetics

Answer: b

Explanation: Diffusivity is defined as the rate of diffusion. It is a measure of particles at which the fluids or heat can spread. They are measured in different mediums. It can be defined on the basis of its properties.

2. Which among the following is the standard symbol for Archimedes number?

a) A

b) AR

c) A r

d) a

Answer: c

Explanation: The standard symbol for Archimedes number is Ar. Archimedes number in fluid mechanics deals with the motion of fluids. This takes place due to the differences in their densities. It was followed by the Archimedes principle.

3. The Prandtl Number approximates ___________

a) Momentum diffusivity to thermal diffusivity

b) Thermal diffusivity to momentum diffusivity

c) Shear stress to thermal diffusivity

d) Thermal diffusivity to kinematic viscosity

Answer: a

Explanation: The Prandtl number is a dimensionless number. It approximates the ratio of momentum diffusivity to thermal diffusivity. It can be expressed as P r = v/ α. Where α= thermal diffusivity and v= momentum diffusivity.

4. Which among the following is the standard symbol for Atwood number?

a) A

b) AR

c) A r

d) a

Answer: a

Explanation: The standard symbol for Atwood number is A. Atwood’s number in fluid mechanics deals with the onset of instabilities in mixtures of fluid. It is due to the density differences in fluid.

5. Which among the following is the standard symbol for Blake number?

a) Bi

b) ba

c) Bl

d) b

Answer: b

Explanation: The standard symbol for Blake number is B or Bl. Blake number in fluid mechanics deals with geology, fluid mechanics and porous media. It is due to the inertial over the viscous forces in fluid flow through porous media.

6. Which among the following is the standard symbol for Darcy friction factor?

a) F

b) F d

c) C

d) C d

Answer: b

Explanation: The standard symbol for Darcy friction factor is F d . Darcy friction factor in fluid mechanics deals with fractions of pressure losses. This is due to the development of friction in the pipe.

7. Fanning friction factor is _________

a) 0.25 times Darcy friction factor

b) Same as Darcy friction factor

c) 2 times Darcy friction factor

d) Independent

Answer: a

Explanation: Fanning friction factor is 0.25 times Darcy friction factor. Fanning friction factor in fluid mechanics deals fraction of pressure losses due to friction in the pipe.

8. Which among the following is the standard symbol for Froude number?

a) F

b) Fo

c) F r

d) f

Answer: c

Explanation: The standard symbol for Froude number is F r . Froude number in fluid mechanics deals with wave and surface behaviour of fluid particles. This is with the ratio of body’s inertia to gravitational forces.

9. Which among the following is the standard symbol for Peclet number?

a) P

b) p

c) Pe

d) pe

Answer: c

Explanation: The standard symbol for Peclet’s number is Pe. Peclet’s number in fluid mechanics deals with heat transfer. It is defined as the ratio of transport rate over molecular diffusive transport.

10. Which among the following is the formula for Knudsen number?

a) λ ⁄ L

b) λ ⁄ 2L

c) λ ⁄ 3L

d) λ ⁄ 4L

Answer: a

Explanation: The formula for Knudsen number is λ ⁄ L . Knudsen number in fluid mechanics deals with gas dynamics. It is defined as the ratio of the molecular mean free path length to the representative scale length.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Turbulent Boundary Layer on a Flat Plate”.

1. The main property that affects a boundary layer is__________

a) Temperature

b) Pressure

c) Viscosity

d) Surface tension

Answer: c

Explanation: A boundary layer is an important concept that refers to the layer of fluid. The fluid that is in the immediate vicinity of a bounding surface. The main property that affects a boundary layer is viscosity.

2. The layer that is influenced by a planetary boundary is called______

a) Atmospheric boundary layer

b) Lithosphere

c) Troposphere

d) Hydrosphere

Answer: a

Explanation: The planetary boundary layer is also called as atmospheric boundary layer. It is the lowest part of the atmosphere. The behaviour of ABL is directly influenced by its contact with the planetary surface.

3. What is the other name for Stoke’s boundary layer?

a) Momentum boundary layer

b) Atmospheric boundary layer

c) Oscillatory boundary layer

d) Thermal boundary layer

Answer: c

Explanation: Stoke’s boundary layer is also called as Oscillatory boundary layer. It is a boundary layer that is close to a solid wall. It moves in an oscillatory motion. It arrested by a viscous force acting in the opposite direction.

4. Eddy viscosity is a turbulent transfer of_________

a) Fluid

b) Heat

c) Momentum

d) Pressure

Answer: c

Explanation: Eddy viscosity is a turbulent transfer of momentum by eddies. It gives rise to an internal fluid friction. It is in analogous to the action of molecular viscosity in laminar fluid flow. Eddy viscosity takes place on a large scale.

5. The laminar boundary layer is a _________

a) Smooth flow

b) Rough flow

c) Uniform flow

d) Random flow

Answer: a

Explanation: For a laminar boundary layer the fluid moves in a very smooth flow. The laminar flow creates less skin friction drag. It is a less stable flow. The laminar boundary layer has got an increase in its thickness.

6. The turbulent boundary layer is a _________

a) Non-uniform with swirls

b) Uniform

c) Less stable

d) Smooth

Answer: a

Explanation: For a turbulent boundary layer the fluid moves in different direction producing swirls. It has more skin friction drag than that of laminar boundary layer. It is more stable when compared to laminar.

7. How do we measure the flow rate of liquid?

a) Coriolis method

b) Dead weight method

c) Conveyor method

d) Ionization method

Answer: a

Explanation: Coriolis concept of measurement of fluid takes place through the rotation with the reference frame. It is an application of the Newton’s Law. The device continuously records, regulates and feeds large volume of bulk materials.

8. How does a turbulent boundary layer produce swirls?

a) Due to random motion

b) Collision of molecules

c) Due to eddies

d) Due to non-uniform cross section

Answer: c

Explanation: For a turbulent boundary layer the fluid moves in different direction producing swirls. It produces swirls due to the presence of eddies. The smooth laminar boundary layer flow breaks down and transforms to a turbulent flow.

9. Define Viscosity.

a) Resistance to flow of object

b) Resistance to flow of air

c) Resistance to flow of fluid

d) Resistance to flow of heat

Answer: c

Explanation: Viscosity is developed due to the relative motion between two surfaces of fluids at different velocities. It happens due to the shear stress developed on the surface of the fluid.

10. The continuity equation of two- dimensional steady incompressible flow is_______

fluid-mechanics-questions-answers-turbulent-layer-plate-q10

Answer: a

Explanation: The continuity equation of two- dimensional steady incompressible flow is fluid-mechanics-questions-answers-turbulent-layer-plate0q10-exp . It is in accordance with the Navier- Stokes equations for a two- dimensional steady incompressible flow in cartesian coordinates.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Separation of Boundary Layer”.

1. How can we determine whether the flow is laminar or turbulent?

a) Reynold’s number

b) Mach number

c) Froude number

d) Knudsen number

Answer: a

Explanation: Reynold’s number is used to determine whether the flow is laminar or turbulent. If Reynold’s number is less than 2000, it is a laminar flow. If Reynold’s number is greater than 2000, then it is a turbulent flow.

2. The flow separation occurs when the fluid travels away from the __________

a) Surface

b) Fluid body

c) Adverse pressure gradient

d) Inter-molecular spaces

Answer: c

Explanation: Adverse pressure gradient takes place when the static pressure increases. It increases the direction of the flow. Adverse pressure gradient plays an important role in flow separation. Thus, option c is correct.

3. The swirl caused due to eddies are called as ______

a) Vortices

b) Vertices

c) Volume

d) Velocity

Answer: a

Explanation: Vortices are a region in a fluid. It takes place when the flow revolves around an axis line. Vortices can be straight or curved. They form shapes like smoke rings and whirlpools.

4. Eddy viscosity is a turbulent transfer of_________

a) Fluid

b) Heat

c) Momentum

d) Pressure

Answer: c

Explanation: Eddy viscosity is a turbulent transfer of momentum by eddies. It gives rise to an internal fluid friction. It is in analogous to the action of molecular viscosity in laminar fluid flow. Eddy viscosity takes place on a large scale.

5. Which among the following is a device that converts a laminar flow into a turbulent flow?

a) Dead Weight Gauge

b) Vacuum Gauge

c) Turbulator

d) Ionization Gauge

Answer: c

Explanation: Turbulator is a device that converts a laminar flow into a turbulent flow. The turbulent flow can be desired parts of an aircraft or also in industrial applications. Turbulator is derived from the word “turbulent”.

6. Boundary layer separation does not undergo detachment.

a) True

b) False

Answer: b

Explanation: Boundary layer separation undergoes detachment from the surface into a broader wake. It occurs mainly when the portion of the boundary layer is closest to the wall. It leads to reverse in the flow direction.

7. With the boundary layer separation, displacement thickness________

a) Increases

b) Decreases

c) Remains Same

d) Independent

Answer: a

Explanation: With the boundary layer separation, displacement thickness increases sharply. This helps to modify the outside potential flow and its pressure field. Thus, option ‘a’ is the correct choice.

8. What is the instrument used for the automatic control scheme during the fluid flow?

a) Rotameters

b) Pulley plates

c) Rotary Piston

d) Pilot Static Tube

Answer: d

Explanation: Pilot static tube is a system that uses an automatic control scheme to detect pressure. It has several holes connected to one side of the device. These outside holes are called as a pressure transducer, which controls the automatic scheme during fluid flow.

9. What is D’Alembert’s Paradox?

a) Resistance= 0

b) Drag force= 0

c) Temperature = 0

d) Pressure gradient= 0

Answer: b

Explanation: D’Alembert’s Paradox states that for an incompressible and inviscid flow potential flow, the drag force is equal to zero. The fluid is moving at a constant velocity with respect to its relative fluid.

10. The steady- state flow must satisfy ___________

a) Kirchhoff’s law

b) Newtons law

c) Rutherford’s experiment

d) Kepler’s law

Answer: a

Explanation: The steady state flow must satisfy Kirchhoff’s first and second law. The first law states that the total flow into the junction equals the total flow away from the junction. Second law is called as the law of conservation of mass. It states that between two junctions, the head loss is independent of the path followed.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Drag on a Sphere”.

1. What is the dimension for drag coefficient?

a) Newton/s

b) m/s

c) kg/N

d) Dimensionless

Answer: d

Explanation: In fluid dynamics, the drag coefficient has no dimensions. It is a dimensionless quantity. Drag coefficient is used to quantify the resistance of an object in a fluid environment. It is mainly used in air and water.

2. Skin friction acts on the component of _________

a) Profile drag

b) Surface blade

c) Vane angles

d) Parallel movement

Answer: a

Explanation: Skin friction acts on the component of profile drag. Pressure drag is also called as form drag. It mainly arises because of the shape of the object. Thus, the correct answer is profile drag.

3. Bodies with a larger cross section will have________

a) Lower drag

b) Higher drag

c) Same drag

d) No drag

Answer: b

Explanation: Bodies with a larger cross section will have higher drag. Pressure drag is also called as form drag. It mainly arises because of the shape of the object. Thus, the correct option ‘b’.

4. Drag coefficient is denotes as_______

a) C d

b) B c

c) D c

d) T c

Answer: a

Explanation: In fluid dynamics, the drag coefficient has no dimensions. It is a dimensionless quantity. Drag coefficient is used to quantify the resistance of an object in a fluid environment. It is mainly used in air and water. It is denoted as C d .

5. The drag coefficient of a complete structure such as an aircraft includes________

a) Form drag

b) Pressure drag

c) Interference drag

d) Induced drag

Answer: c

Explanation: The drag coefficient of a complete structure such as an aircraft includes interference drag. It results when an airflow around one part of an object. The two airflows must speed up in order to pass through the restricted area.

6. The drag coefficient is directly proportional to the ___________

a) Drag force

b) Mass density

c) Area

d) Flow speed

Answer: a

Explanation: The drag coefficient is directly proportional to the drag force. In fluid dynamics, the drag coefficient has no dimensions. It is a dimensionless quantity. Drag coefficient is used to quantify the resistance of an object in a fluid environment.

7. If the friction is neglected, then_______

a) V r1 > V r2

b) V r1 < V r2

c) V r1 = V r2

d) V r1 is a zero

Answer: c

Explanation: The relative velocity of the jet is denoted as V r1 . It is the relative velocity at the inlet to the vane. Relative velocity of inlet to the vane is obtained by subtracting vectorially the velocity of the vane with its absolute velocity. It happens in the same way for V r2 . Thus, If the friction is neglected, then V r1 = V r2 .

8. Drag force is directly proportional to ________

a) Density of fluid

b) Mass density

c) Area

d) Flow speed

Answer: a

Explanation: Drag force is directly proportional to density of the fluid. It is the force that acts opposite to the relative motion of any object moving with respect to its surroundings. Thus, the correct option is ‘a’.

9. Drag force can exist between two layers of liquid.

a) True

b) False

Answer: a

Explanation: Drag force can exist between two layers of liquid. They can even exist in between two layers of solid surface. Unlike other resistive forces, they are dependent on velocity.

10. The efficiency of the vane is given by_________

a) 1-V 2 2 / V 1 2

b) 1-(V 2 2 / V 1 2 )

c) V 2 2 / V 1 2

d) 1- V 1 2

Answer: a

Explanation: In a velocity triangle at the inlet and the outlet, the control volume is moving with a uniform velocity. Therefore, the momentum theorem of the control volume is at a steady flow. Thus, the efficiency of the vane is given by 1-(V 2 2 / V 1 2 ).

11. Drag coefficient is a function of _________

a) Mach number

b) Froude’s number

c) Laminar flow

d) Reynolds number

Answer: a

Explanation: Drag coefficient is a function of Mach number. In fluid dynamics, the drag coefficient has no dimensions. It is a dimensionless quantity. Drag coefficient is used to quantify the resistance of an object in a fluid environment.

12. For a streamlined body to achieve low drag coefficient, the boundary layer must_________

a) Flow over the body

b) Be attached to the body

c) Move away from the body

d) Move parallel to the body

Answer: b

Explanation: For a streamlined body to achieve low drag coefficient, the boundary layer must be attached to the surface of the body for a long time as possible. This causes the wake to be narrow.

13. There will be a transition from laminar flow to turbulent flow when______

a) Reynolds number increases

b) Reynolds number decreases

c) Reynolds number is the same

d) Froude’s number increases

Answer: a

Explanation: There will be a transition from laminar flow to turbulent flow with the increase in the Reynolds number. Reynolds number below 2000 is laminar flow and Reynolds number above 2000 is for turbulent flow.

14. With the increase in flow velocity, Reynolds number_________

a) Increases

b) Decreases

c) Same

d) Independent

Answer: a

Explanation: With the increase in flow velocity, Reynolds number increases. Reynolds number below 2000 is laminar flow and Reynolds number above 2000 is for turbulent flow. Thus, the correct option is Increases.

15. With the decrease in the viscosity, Reynolds number ________

a) Increases

b) Decreases

c) Same

d) Independent

Answer: a

Explanation: With the decrease in viscosity, Reynolds number increases. Reynolds number below 2000 is laminar flow and Reynolds number above 2000 is for turbulent flow. Thus, the correct option is Increases.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Thermodynamic Relations”.

1. The symbol of Helmholtz free energy is_________

a) A

b) H

c) B

d) E

Answer: a

Explanation: Helmholtz free energy is defined as the thermodynamic potential that measures the useful work obtained from a closed thermodynamic system. It is done at a constant volume and temperature. IUPAC name is ‘A’.

2. Which among the following is the formula for Helmholtz free energy?

a) U+TS

b) U+TV

c) U-TS

d) UTV

Answer: c

Explanation: Helmholtz free energy is defined as the thermodynamic potential that measures the useful work obtained from a closed thermodynamic system. It is done at a constant volume and temperature. IUPAC name is ‘A’. .

3. What is the unit of Helmholtz free energy?

a) Kelvin

b) Joule

c) Kilowatt

d) Newton

Answer: b

Explanation: Helmholtz free energy is defined as the thermodynamic potential that measures the useful work obtained from a closed thermodynamic system. The SI unit of Helmholtz free energy is Joule.

4. What is the symbol for Gibbs free energy?

a) A

b) H

c) G

d) E

Answer: c

Explanation: Gibbs free energy is defined as the thermodynamic potential that is used to calculate the maximum amount of reversible work. It takes place at a constant pressure and temperature. The IUPAC name for Gibbs free energy is ‘G’.

5. Gibbs free energy is also known as______

a) Free energy

b) Free entropy

c) Free enthalpy

d) Free motion

Answer: c

Explanation: Gibbs free energy is defined as the thermodynamic potential that is used to calculate the maximum amount of reversible work. Gibbs free energy is also known as free enthalpy. It takes place at a constant pressure and temperature.

6. What is the unit of Gibbs free energy?

a) Kelvin

b) Joule

c) Kilowatt

d) Newton

Answer: b

Explanation: Gibbs free energy is defined as the thermodynamic potential that is used to calculate the maximum amount of reversible work. It takes place at a constant pressure and temperature. The SI unit is Joule.

7. Which among the following is the formula for Gibbs free energy?

a) H-T∆S

b) H-T

c) T∆S

d) H-S

Answer: a

Explanation: Gibbs free energy is defined as the thermodynamic potential that is used to calculate the maximum amount of reversible work. It takes place at constant temperature and pressure. It is given by H-T∆S.

8. All the energy relations satisfy the mathematical condition in thermodynamics.

a) True

b) False

Answer: a

Explanation: All the thermodynamic energy relations satisfy the mathematical condition of being a set of continuous variables. They are a function of state variables themselves.

9. The performance of a flow device is expressed in terms of _________

a) Adiabatic efficiency

b) Isentropic efficiency

c) Thermal efficiency

d) Mechanical efficiency

Answer: b

Explanation: The performance of a flow device is expressed in terms of its isentropic efficiency. The actual performance of the device is compared with that of its isentropic device. It happens at the same inlet and exit conditions.

10. Isentropic efficiency is defined as ________

a) The power output of actual turbine/ power output if the turbine were isentropic

b) The power input of actual turbine/ power output if the turbine were isentropic

c) The power output of actual turbine/ power output if the turbine were adiabatic

d) The power output of actual turbine/ power output if the turbine were polytropic

Answer: a

Explanation: The performance of a flow device is expressed in terms of its isentropic efficiency. The actual performance of the device is compared with that of its isentropic device. It happens at the same inlet and exit conditions.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Basic Equations of Compressible Flow”.

1. Which among the following is the formula for continuity equation?

a) ρVA = Constant

b) A = Constant

c) ρV = constant

d) PV = constant

Answer: a

Explanation: Continuity equation for a steady one-dimensional flow is ρVA = Constant. Where ρ = Density of the fluid flow. V = the volume of the fluid flow. And, A = Area of the fluid flow through the cross section of pipe.

2. What is v 2 /2 in the equation for a control volume in space?

a) Potential energy per unit mass

b) Kinetic energy per unit mass

c) Thermal energy per unit mass

d) Mechanical energy per unit mass

Answer: b

Explanation: According to the first law of thermodynamics, the equation for control volume in space is derived. v 2 /2 in the equation for a control volume in space is the kinetic energy per unit mass. Therefore, option b is the right choice.

3. Sum of enthalpy and kinetic energy remains a constant in __________

a) Polytropic flow

b) Isentropic flow

c) Adiabatic flow

d) Mechanical flow

Answer: c

Explanation: The sum of enthalpy and kinetic energy remains a constant in adiabatic flow. It performs a similar role that internal energy performs during a nonflowing system. Thus, the correct option is Adiabatic flow.

4. Eddy viscosity is a turbulent transfer of _________

a) Fluid

b) Heat

c) Momentum

d) Pressure

Answer: c

Explanation: Eddy viscosity is a turbulent transfer of momentum by eddies. It gives rise to an internal fluid friction. It is in analogous to the action of molecular viscosity in laminar fluid flow. Eddy viscosity takes place on a large scale.

5. Which among the following is the equation for Bernoulli?

a) Tds = dh – vdp

b) Tds = dh

c) Tds = dh + vdp

d) Tds = dh/vdp

Answer: a

Explanation: For an adiabatic frictionless flow, the Bernoulli’s equation is identical to its energy equation. The Bernoulli’s equation after integrating changes to Tds = dh – vdp. Thus, the correct option is a.

6. For an isentropic flow ________

a) Enthalpy = 0

b) Entropy = 0

c) Pressure = 0

d) Temperature = 0

Answer: b

Explanation: For an isentropic flow in Tds = dh – vdp, the entropy reduces to zero. That is, the change in entropy value for any isentropic flow =0. Thus, the correct option is Entropy = 0.

7. Which among the following is Euler’s equation?

a) VdV/dh = 0

b) VdV – dh = 0

c) VdV + dh = 0

d) dh – V = 0

Answer: c

Explanation: The Euler’s equation is given as VdV+dh=0. Where V = volume of the fluid flow and h = enthalpy of the fluid flow. This is identical to the adiabatic form of the energy equation. Thus, the option is VdV + dh = 0.

8. Which among the following is the formula for momentum principle?

a) pv = 0

b) p 1 p 2 = 0

c) P 1 V 1 + P 2 V 2 = 0

d) P 1 A1+P 2 A 2 + F = mV 2 mV 1

Answer: d

Explanation: For a finite control of volume between two sections, section 1 and section 2, the momentum principle is P 1 A 1 + P 2 A 2 + F = mV 2 mV 1 . Where F = component of resultant force exerted on the fluid walls.

9. Define Stagnation temperature.

a) The temperature at zero velocity

b) The temperature at zero pressure

c) The temperature at zero heat transfer

d) The temperature at zero volume

Answer: a

Explanation: The stagnation point is the point at which the properties of the fluid are obtained at a local flow where the velocity of the fluid is zero isentropically. Thus, the correct choice for stagnation temperature is ‘a’.

10. What is the viscosity of water at 30 o C?

a) 80.1

b) 0.801

c) 801

d) 0.081

Answer: b

Explanation: A graph is plotted with temperature in the x-axis and dynamic viscosity in the y-axis. With the increase in pressure the viscosity decreases. It corresponds to an informal concept of thickness.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Velocity of Sound or Pressure Wave in a Fluid – 1”.

1. Speed is of sound is the _________

a) Distance travelled per unit length

b) Distance travelled per unit time

c) Distance travelled per unit pressure

d) Distance travelled per unit temperature

Answer: b

Explanation: The speed of sound is defined as the distance travelled per unit time. It is due to the sound wave. The sound wave propagates through the medium.

2. The sound wave is transmitted through liquids as_________

a) Longitudinal waves

b) Transverse waves

c) Elongated waves

d) Refracted waves

Answer: a

Explanation: The sound wave is transmitted through liquids, gases and plasma as longitudinal waves. It is also called as compressed waves. Longitudinal waves require a medium to propagate. Thus, the correct answer is Longitudinal waves.

3. What are the assumptions made for a fluid flow through a pipe?

a) Fluid inertia is not taken

b) Viscosity is not taken

c) Volume is not considered

d) Mass is not considered

Answer: a

Explanation: During a fluid flow through a pipe, there are various design considerations. But, the two major assumptions are that the flow is assumed to be fully developed. Also, fluid inertia is not taken into account.

4. Which among the following is not generic property of sound?

a) Viscosity

b) Amplitude

c) Direction

d) Frequency

Answer: a

Explanation: Viscosity is not a generic property sound. It is defined as the property of resistance to flow of fluid. Resistance to flow of fluid takes place when one layer of fluid slides over the other. Viscosity is not a generic property.

5. Sound perceptible by humans has frequencies from _______

a) 20 to 2000 Hz

b) 20 to 20000 Hz

c) 10 to 10000 Hz

d) 30 to 30000 Hz

Answer: b

Explanation: Sounds that are audible to a human ear ranges from 20 to 20000 Hz. At standard temperature and pressure of air, the corresponding wavelengths of sound range from 17m to 17mm.

6. What is the speed of sound in dry air?

a) 331.2 m/s

b) 300 m/s

c) 250 m/s

d) 230 m/s

Answer: a

Explanation: The speed of sound in dry air at a temperature of zero degrees Celsius is equal to 331.2 m/s. Speed of sound in air is denoted by the symbol ‘c’. Thus the correct answer for the following is 331.2 m/s.

7. What is the speed of sound at 20 o C?

a) 331.2 m/s

b) 350 m/s

c) 343 m/s

d) 300 m/s

Answer: c

Explanation: The speed of sound in dry air at a temperature of 20 o C is equal to 343 m/s. It is found out using the relation of kilometre and miles. One kilometre = 2.91 seconds, and one mile = 4.69 seconds.

8. Speed of sound in an ideal gas depends on _______

a) Temperature and pressure

b) Surface area and volume

c) Temperature and composition

d) Composition and surface area

Answer: c

Explanation: Speed of sound in ideal gas depends on its composition and temperature. The speed of sound has a weak dependence on frequency and pressure. As there is a slight deviating behaviour in an ideal fluid.

9. Transverse wave is also called as ________

a) Shear wave

b) Compression wave

c) Compressed wave

d) Longitudinal wave

Answer: a

Explanation: Transverse wave is also called as a shear wave. Transverse wave or shear waves occur only in solids. It occurs only in solids because only solids support elastic deformations. It is also called as an elastic wave.

10. Which among the following determines the geometric orientation of transverse waves?

a) Dichroism

b) Optical activity

c) Polarization

d) Photon spin

Answer: c

Explanation: Polarization is defined as a property applied to transverse waves or shear waves. The main function of polarization is to determine the geometric orientation of transverse waves or shear waves.

This set of Fluid Mechanics Puzzles focuses on “Velocity of Sound or Pressure Wave in a Fluid – 2”.

1. A wave that has propagating disturbance is called ________

a) Shock wave

b) Compression wave

c) Compressed wave

d) Longitudinal wave

Answer: a

Explanation: Shock wave is defined as the wave that has a propagating disturbance. When the propagating wave move faster than the local speed of fluid, it is called as a shock wave. It can propagate through any medium.

2. A shock wave carries _______

a) Heat

b) Pressure

c) Energy

d) Temperature

Answer: c

Explanation: The shock wave carries energy and can propagate through a medium. It can be characterized as abrupt. It is due to the discontinuous changes in pressure, density and temperature of the medium.

3. Shock waves can be normal, oblique and bow.

a) True

b) False

Answer: a

Explanation: Shock waves can be at normal angles, oblique angles and bow angles. Normal angle is perpendicular to the shock medium’s flow direction. Oblique angle is at the direction of flow. Bow occurs at the front of the object.

4. Bow occurs at what Mach number?

a) Mach number = 0

b) Mach number is negative

c) Mach number = 1

d) Mach number greater than 1

Answer: d

Explanation: Bow occurs when the Mach number is greater than one. It occurs at the upstream of the front of a blunt object. It happens when the velocity exceeds Mach 1.

5. A boundary over which physical conditions undergo changes is called _______

a) Shear front

b) Shock front

c) Contact front

d) Cap front

Answer: b

Explanation: Shock front is defined as the boundary over which the physical conditions of a fluid undergo abrupt changes. This happens due to the shock wave. Thus, the correct choice is option Shock front.

6. A shock wave caused by driver gas is called _______

a) Shear front

b) Shock front

c) Contact front

d) Cap front

Answer: c

Explanation: Contact front is defined as a shock wave caused by a driver gas. It is the boundary layer between the driver gases and the driven gases. The main function of the contact front is to trails the shock front.

7. When the fluid flow is discontinuous, what is established?

a) Heat

b) Pressure

c) Control volume

d) Temperature

Answer: c

Explanation: When the fluid flow is discontinuous, a control volume is established. It is established around the shock wave. It is treated as a discontinuity where the entropy increases to over a infinitesimally large region.

8. Shock waves that deviate from the arbitrary angle are called_______

a) Oblique shock

b) Bow shock

c) Normal shock

d) Detonation

Answer: a

Explanation: Shock waves in a flow field which are attached to a body start deviating at some arbitrary angle from the flow direction of the fluid. This shock so developed due to angle deviation is called as oblique shock.

9. When a shock wave forms continuous pattern, it is called ________

a) Oblique shock

b) Bow shock

c) Normal shock

d) Detonation

Answer: b

Explanation: Bow occurs when the Mach number is greater than one. It occurs at the upstream of the front of a blunt object. It happens when the velocity exceeds Mach 1. When a shock wave forms continuous pattern, it is called a bow shock.

10. Shocks generated due to an interaction of two bodies are called ______

a) Oblique shock

b) Bow shock

c) Moving shock

d) Detonation

Answer: c

Explanation: Shocks that are generated by the interaction of two bodies of gas. This interaction takes place at different pressure, with the shock wave propagating into a lower pressure gas and an expansion wave propagates into a high-pressure gas.

11. Shocks generated due to trailing exothermic reaction is called ______

a) Oblique shock

b) Bow shock

c) Moving shock

d) Detonation

Answer: d

Explanation: Shocks that are generated due to trailing exothermic reaction is called as detonation. It is a wave traveling through a medium of highly combustible and chemically unstable medium.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Stagnation Properties”.

1. __________ is referred as the temperature at a stagnation point in the flow of fluids in fluid mechanics and thermodynamics.

a) Absolute temperature

b) Maximum temperature

c) Stagnation temperature

d) Hydraulic temperature

Answer: c

Explanation: Stagnation temperature is the temperature at the stagnation point of the flow of fluids. In thermodynamics and fluid mechanics, these terms find application. At a stagnation point the speed of the fluid is zero and all of the kinetic energy has been converted to internal energy and is added to the local static enthalpy.

2. In ________ and _______ kind of flow, the stagnation temperature is equal to the total temperature

a) compressible, incompressible

b) stagnated, non-stagnated

c) dynamic, non-dynamic

d) turbulent, passive

Answer: a

Explanation: In compressible and incompressible kind of flow, the stagnation temperature is equal to the total temperature. This occurs at all points on the streamline. Eventually, this leads to the stagnation point.

3. _____ is the law employed in the derivation of stagnation point.

a) Hooke’s law

b) Poisson’s law

c) Second law of thermodynamics

d) First law of thermodynamics

Answer: d

Explanation: First law of thermodynamics is the law employed in the derivation of stagnation point. It states that the change in the internal energy ΔU of a closed system is equal to the amount of heat Q supplied to the system, subtracting the amount of work W done by the system on its surroundings. It is a modified form of the law of conservation of energy.

4. A bimetallic ________ is generally utilized to measure stagnation temperature

a) Transistor

b) Thermometer

c) Diode

d) Thermocouple

Answer: d

Explanation: A bimetallic thermocouple is generally utilized to measure stagnation temperature. However, there must be allowances for thermal radiation. This is done in order to avoid the occurrence of errors.

5. Stagnation point is the point in fluid mechanics where the velocity of the fluid at that point is _____

a) zero

b) infinite

c) constant

d) unity

Answer: a

Explanation: Stagnation point is the point in fluid mechanics where the velocity of the fluid at that point is zero. Stagnation points occur at places where the fluid is brought to a state of rest by an object. They usually exist at the surface of objects.

6. _________ proves that the static pressure is maximum when the velocity is zero

a) Laws of Thermodynamics

b) Bernoulli’s Equation

c) Hooke’s law

d) Principle of continuity

Answer: b

Explanation: Bernoulli’s equation proves that the static pressure is maximum when the velocity is zero. Bernoulli’s principle states that a rise in the speed of a fluid occurs simultaneously with a drop in pressure or a drop in the fluid’s potential energy. It is named after Daniel Bernoulli, who stated it.

7. Total pressure is an addition of static pressure and ______

a) Dynamic pressure

b) Stagnation pressure

c) Fluid pressure

d) Instantaneous pressure

Answer: a

Explanation: Total pressure is an addition of static pressure and dynamic pressure. In incompressible flow, the stagnation pressure is equal to the sum of dynamic pressure and static pressure. So here, stagnation pressure is equal to total pressure.

8. The pressure coefficient at a stagnation point is _____

a) +1

b) -1

c) 0

d) Infinite

Answer: a

Explanation: The pressure coefficient at a stagnation point is unity. This is referred to as +1. A pressure coefficient is a dimensionless number which describes the relative pressures throughout a flow field in fluid dynamics.

9. _________ minus freestream static pressure gives freestream dynamic pressure

a) Stagnation pressure

b) Total pressure

c) Fluid pressure

d) Instantaneous pressure

Answer: a

Explanation: Stagnation pressure minus freestream static pressure gives freestream dynamic pressure. This plays an important role in determining the pressure coefficient. Hence, the pressure coefficient at stagnation points is +1.

10. On a streamlined body fully immersed in a potential flow, there are ____ stagnation points

a) 1

b) 2

c) 0

d) Infinite

Answer: b

Explanation: On a streamlined body fully immersed in a potential flow, there are 2 stagnation points. One point is present near the leading edge. The other point is present near the trailing edge.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Area Velocity Relationship for Compressible Flow”.

1. The exit velocity in the nozzle increases as per __________

a) Stagnation point

b) Continuity equation

c) Prandtl Number

d) Newton’s law

Answer: b

Explanation: In the nozzle, the exit velocity of the fluid increases as per the continuity equation. Continuity equation is given as Av= constant as per the Bernoulli’s equation. It is essential for an incompressible flow.

2. With the increase in pressure, the exit velocity _________

a) Decreases

b) Increases

c) Same

d) Independent

Answer: a

Explanation: Pressure is inversely proportional to the velocity. So, with the increase in pressure, the exit velocity decreases. We know that the pressure is equal to force per unit area, this contradicts the above statement.

3. The Prandtl Number approximates ___________

a) Momentum diffusivity to thermal diffusivity

b) Thermal diffusivity to momentum diffusivity

c) Shear stress to thermal diffusivity

d) Thermal diffusivity to kinematic viscosity

Answer: a

Explanation: The Prandtl number is a dimensionless number. It approximates the ratio of momentum diffusivity to thermal diffusivity. It can be expressed as P r = v/ α. Where α= thermal diffusivity and v= momentum diffusivity.

4. Pumps increase __________

a) Pressure

b) Velocity

c) Momentum

d) Heat

Answer: a

Explanation: Pumps increase pressure rather than velocity. During the pumping process, a housing is provided for the pumping elements. These parts can change the speed. Pumps create a passage way that will squirt the fluid passing through it. Thus, pumping increases pressure.

5. Which among the following is the formula for volumetric flow rate?

a) Q = v/A

b) Q = Av

c) Q = A+v

d) Q = A-v

Answer: b

Explanation: Volumetric flow rate is given by Q= A.v. Where v is the flow velocity of the fluid, and A is the area of cross section of the surface. Area of a surface is also called as the vector area. Thus, the right answer is Q = Av.

6. Which among the following is the formula for mass flow rate?

a) Q = m/p

b) Q = mp

c) Q = m + p

d) Q = m – p

Answer: b

Explanation: Mass flow rate is given by Q=m/p. This is a relation expressed for mass flow rate. When ‘m’ is the mass flow rate. And, p is the density of the fluid flow. They are expressed in their standard units.

7. Compressible flow is a flow that deals with ______

a) Fluid temperature

b) Fluid pressure

c) Fluid density

d) Fluid geometry

Answer: c

Explanation: Compressible flow is a branch of fluid mechanics that deals with different types of flow. Its main significance lies in the change in fluid density. Thus, the correct option is Fluid density .

8. Compressible flow mainly deals with _______

a) Solid dynamics

b) Liquid dynamics

c) Gas dynamics

d) Solid and liquid dynamics

Answer: c

Explanation: Compressible flow is a branch of fluid mechanics that deals with different types of flow. Its main significance lies in the change in fluid density. It deals with gas dynamics.

9. Which among the following is an assumption of the compressible flow?

a) Resistance to flow of object

b) No-slip condition

c) Known mass flow rate

d) Resistance to flow of heat

Answer: b

Explanation: The related assumption of a compressible fluid flow is No-slip condition. It is assumed that the flow velocity at the solid surface is equal to the velocity of the surface itself. It is in direct consequence with the continuum flow.

10. What is Mach number?

a) Speed of object * speed of sound

b) Speed of object /speed of sound

c) Speed of object + speed of sound

d) Speed of object- speed of sound

Answer: b

Explanation: Mach number is defined as the ratio of the speed of an object to the speed of sound. Mach number is denoted by ‘M’. Mach number ranges from zero to infinity. It falls into several flow regimes.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Flow of Compressible Fluid through Orifices and Nozzles”.

1. What is the Mach number at room temperature?

a) 310 m/s

b) 320 m/s

c) 330 m/s

d) 340 m/s

Answer: d

Explanation: Mach number is defined as the ratio of the speed of an object to the speed of sound. Mach number is denoted by ‘M’. Mach number ranges from zero to infinity. It falls into several flow regimes. It is 340 m/s at room temperature.

2. In a one-dimensional flow, the gas flows through one spatial dimension, namely its length.

a) True

b) False

Answer: a

Explanation: One dimensional flow refers to the flow of gas through a duct or channel in which the flow parameters are assumed to change significantly along a particular dimension. In this case, it’s about its duct length.

3. The compressible flow is assumed to be _____________

a) Isentropic

b) Adiabatic

c) Polytropic

d) Isentropic and adiabatic

Answer: a

Explanation: Compressible flow is a branch of fluid mechanics that deals with different types of flow. Its main significance lies on the change in fluid density. It deals with gas dynamics. Flow is assumed to be isentropic.

4. Ratio of duct length to width length in a compressible flow is_______

a) More than 5

b) Less than 5

c) More than or equal to 5

d) Less than or equal to 5

Answer: d

Explanation: In a compressible flow, the flow is usually in a single dimension. One dimensional flow refers to the flow of gas through a duct or channel in which the flow parameters are assumed to change significantly. Thus, it is less than or equal to 5.

5. The fluid speed through the nozzle is altered with________

a) Acceleration

b) Deceleration

c) Constant speed

d) Zero

Answer: a

Explanation: The fluid speed through the nozzle is altered as the speed accelerates from subsonic speed to supersonic speed in a regime. It alters a nozzle and a diffuser.

6. What happens to velocity in the converging duct?

a) Increases

b) Decreases

c) Same

d) Independent

Answer: a

Explanation: Mass flow rate is given by Q = m/p. This is a relation expressed for mass flow rate. With the presence of a converging duct, the velocity increases. At this point, the area of the duct is less than zero.

7. What happens to velocity in the diverging duct?

a) Increases

b) Decreases

c) Same

d) Independent

Answer: b

Explanation: Mass flow rate is given by Q = m/p. This is a relation expressed for mass flow rate. With the presence of a converging duct, the velocity decreases. At this point, the area of the duct is more than zero.

8. The area of the duct is either maximum or minimum when the_________

a) Mach number = 1

b) Mach > 1

c) Mach = 0

d) Mach < 0

Answer: a

Explanation: Mass flow rate is given by Q = m/p. This is a relation expressed for mass flow rate. The area of the duct is either maximum or minimum when the Mach number of the fluid flow is exactly one.

9. Which among the following is an assumption of the compressible flow?

a) Resistance to flow of object

b) No-slip condition

c) Known mass flow rate

d) Resistance to flow of heat

Answer: b

Explanation: The related assumption of a compressible fluid flow is No-slip condition. It is assumed that the flow velocity at the solid surface is equal to the velocity of the surface itself. It is in direct consequence of the continuum flow.

10. Which among the following is an example of a converging-diverging nozzle?

a) De Laval nozzle

b) High velocity nozzle

c) Magnetic nozzle

d) Vacuum nozzle

Answer: a

Explanation: De-Laval nozzle is an example of a converging diverging nozzle. It a tube that is pinched in the mid marking with a particular balance. It is used to accelerate, hot pressurized gases that pass through a higher supersonic speed in the axial thrust.

11. Maximum achievable velocity of a gas is directly proportional to__________

a) Specific heat

b) Deceleration

c) Velocity

d) Pressure

Answer: a

Explanation: Maximum achievable velocity of a gas is directly proportional to the specific heat of gas. It is based on the energy content. It is derived in accordance with the law of conservation of energy.

12. How much pressure ratio makes one Mach number?

a) 0

b) 1

c) 2

d) 3

Answer: c

Explanation: The overall pressure ratio is given by Pb/Pt. The overall pressure ratio must be approximately 2 to attain the Mach number of one. It is because of the changes in the downstream and upstream of flow in the nozzle.

13. Normal shock waves are_______ to the local flow.

a) Parallel

b) Perpendicular

c) Same

d) Independent

Answer: b

Explanation: Normal shock waves are perpendicular to the local flow direction. The shock waves occur when the pressure builds up into an extremely thin shockwave that converts energy into heat. The waves thus take over one another.

14. Oblique shock waves are ______ to the local flow.

a) Parallel

b) Perpendicular

c) Less than 90 degrees

d) Independent

Answer: a

Explanation: Oblique shock waves have an angle less than 90 degrees with respect to its local flow. They are similar to the normal shock waves. When there is any disturbance to the fluid flow at a non-zero angle oblique shock is formed.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Types of Flow in Channels”.

1. The flow characteristics of a channel does not change with time at any point. What type of flow is it?

a) Steady flow

b) Uniform flow

c) Laminar flow

d) Turbulent flow

Answer: a

Explanation: The flow characteristics unchanged with time is a steady flow, characteristics unchanged with space is a uniform flow. Laminar and turbulent flows are classified with reference to Reynolds number.

2. The Reynolds number for a flow in a channel is 1000. What type of flow is it?

a) Laminar

b) Turbulent

c) Transition

d) Steady

Answer: c

Explanation: Reynolds number – 500 to 600 – Laminar flow

Reynolds number – 500 to 2000 – Transition

Reynolds number – > 2000 – Turbulent flow.

3. The ratio of inertia force and gravitational force is called as ______

a) Reynolds number

b) Stokes number

c) Froude’s number

d) Euler’s number

Answer: c

Explanation: Froude’s number is the ratio of inertia forces and gravitational forces. Froude’s number is used to classify the flow into critical, sub critical and super critical.

4. The Froude’s number for a flow in a channel section is 1. What type of flow is it?

a) Sub Critical

b) Critical

c) Super critical

d) Tranquil

Answer: b

Explanation: Froude’s number = 1 – Critical flow

Froude’s number < 1 – Sub Critical flow

Froude’s number > – Super Critical flow.

5. What is the Froude’s number for a channel having mean velocity 4.34 m/s and mean hydraulic depth of 3m?

a) 0.4m

b) 0.6m

c) 0.7m

d) 0.8m

Answer: d

Explanation: Froude’s number (F r ) = V/ (gD 2 )

= 4.34/  (3 2 )

= 0.8m.

6. Calculate the mean hydraulic radius for a channel having 20m 2 cross sectional area and 50m of wetted perimeter.

a) 0.4m

b) 0.5m

c) 0.6m

d) 0.7m

Answer: a

Explanation: Hydraulic Radius = A/P

= 20/50

= 0.4m.

7. Calculate the mean hydraulic depth of a channel having top width of 7m and cross sectional area of 35m 2 .

a) 4m

b) 5m

c) 6m

d) 7m

Answer: b

Explanation: Hydraulic depth  = A/T

= 35/7

= 5m.

8. Estimate the section factor for a channel section having cross sectional area of 40m 2 and hydraulic depth of 6m.

a) 94.3

b) 95.6

c) 97.9

d) 100

Answer: c

Explanation: Section factor  = A√D

= 40√6

= 97.9.

9. Calculate the Froude’s number for a channel having discharge of 261.03m 3 /s, cross sectional area of 42m 2 and the top width being 6m.

a) 0.65

b) 0.72

c) 0.38

d) 0.75

Answer: d

Explanation: F r = V⁄√gD

V = Q/A

V = 261.03/42 = 6.215 m/s

D = A/T = 42/6 = 7m

F r = 0.75 .

10. Calculate the aspect ratio having channel width of 6m and depth of 8m.

a) 0.75m

b) 1.33m

c) 1.50m

d) 1.68m

Answer: b

Explanation: Aspect ratio = Depth / width

= 8/6 = 1.33m.

11. Estimate the type of flow in a channel having cross sectional area of 50m 2 and top of the channel is 5m. The mean velocity of flow is 0.1m/s and the absolute viscosity of water is 0.625 N-s/m 2 .

a) Laminar

b) Turbulent

c) Transition

d) Steady

Answer: c

Explanation: Reynolds number (R e )=1000VD/µ

R e = 1000 / 0.625

D = A/T = 50/5 = 10 m

R e = 1000 / 0.625

= 1600

Transition flow .

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Geometrical Properties of Rectangular Section”.

1. The discharge and velocity of water in a rectangular channel are 75m^3/s and 5m/ s respectively. The hydraulic depth being 3m calculate the hydraulic radius.

a) 1.36m

b) 1.87m

c) 1.98m

d) 2.0m

Answer: a

Explanation: Discharge  =  

75 =  

A = 15m 2

A =  

B = 15/ 3 = 5m

R = A/ P = 15/ )

R = 1.36m.

2. Calculate the hydraulic diameter for a rectangular duct having 10m width and 6m depth.

a) 5.5m

b) 6.5m

c) 7.5m

d) 8.5m

Answer: c

Explanation: Hydraulic diameter = 2By / B + y

Hydraulic diameter = 2  / 16

Hydraulic diameter = 7.5m.

3. The ratio of Hydraulic radius and Hydraulic depth is ½ and the top width of the channel is 6m, calculate the hydraulic depth of the channel.

a) 1m

b) 2m

c) 3m

d) 4m

Answer: c

Explanation: Ratio = ½

Ratio =  /  = T/P; T = 6m

½ = 6/P

P = 12m = B + 2y

12 = 6 + 2y

y = 3m.

4. The section factor of a rectangular channel is 111.80m. The discharge and velocity of water are 250 m 3 ⁄s and 5 m⁄s respectively. Calculate the hydraulic depth of the channel.

a) 2m

b) 3m

c) 4m

d) 5m

Answer: d

Explanation: Section factor  = A√D

Discharge  = AV

A = 250/5 = 50m 2

111.80 = 50√D

D = 5m.

5. The ratio between depth and width of a rectangular channel is ¼ and the area of the rectangular section is 16m^2. Calculate the top width of the channel.

a) 5m

b) 6m

c) 7m

d) 8m

Answer: d

Explanation: Ratio = ¼

D/B = ¼

4D = B

Area  = 16m 2

  = 16 = 4D 2 ; D = 4m

B = 2 = 8m.

6. Which geometric parameter determines the efficiency of the channel?

a) Hydraulic depth

b) Hydraulic radius

c) Section factor

d) Normal depth

Answer: b

Explanation: The Hydraulic Radius is given by R = A/P and as R increases P decreases. As P is less the channel is more efficient.

7. A rectangular channel has depth y and top with B. Determine its section factor.

a) By 3⁄2

b) By 1⁄2

c) By

d) By 2

Answer: a

Explanation: Section factor  = A√D

Z =  √y

Z = By 3⁄2 .

8. Calculate the wetted area for a rectangular channel which is

5.2m in width and 3m in depth.

a) 15.6m 2

b) 16.6m 2

c) 17.6m 2

d) 18.6m 2

Answer: d

Explanation: Wetted area  =   = 15.6m 2 .

9. Calculate the wetted perimeter for a rectangular channel having top width of 4.5m and depth of 3m.

a) 12m

b) 10.5m

c) 7.5m

d) 15m

Answer: b

Explanation: Wetted Perimeter = Width + 2

= 4.5 + 2

= 10.5m.

10. A rectangular channel has a depth of 5m and width of 12m. Calculate the hydraulic depth of the channel.

a) 5m

b) 6m

c) 7m

d) 8m

Answer: a

Explanation: Hydraulic Depth  = Area/Top width

=  / 12

= 5m.

11. The depth and widths of a rectangular channel are 4m and 5m respectively. Determine the hydraulic radius of the channel.

a) 4.22m

b) 3.54m

c) 2.22m

d) 1.54m

Answer: d

Explanation: Hydraulic Radius  = A/P

=  /)

= 1.54m.

12. Determine the section factor for the channel section having area 20m 2 .

a) 20m

b) 30m

c) 40m

d) 50m

Answer: b

Explanation: Section factor  = A√D

= 20√4

= 40m.

13. The section factor and hydraulic depth for a rectangular channel are 40m and 4m respectively. Determine the top width of the channel.

a) 3m

b) 4m

c) 5m

d) 6m

Answer: c

Explanation: Section factor  = A√D

40 = A√4 ; A = 20m 2

A =  

Width = 5m.

14. The hydraulic depth of a rectangular channel is 2m and its wetted area is 12m 2 . Estimate its hydraulic radius.

a) 1.2m

b) 1.3m

c) 1.4m

d) 1.5m

Answer: a

Explanation: Hydraulic Depth  = A/ Top Width

2 = 12/ T

T = 6m

Hydraulic Radius  = A/P

P = T+ 2

P = 6+ 2 = 10m

R = 12/ 10 = 1.2m.

15. Let the top width of a rectangular channel be B and the depth be y, determine the hydraulic radius of the channel.

a) By/ B+2y

b) By/ B+ y

c) y

d) B

Answer: a

Explanation: Hydraulic Radius = A/P

R = / B + 2y.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Geometrical Properties of Triangular Section – 1”.

1. What is the wetted area for a triangular channel having depth y and the side slope being Z?

a) Zy 2

b) 2Zy

c) Zy

d) Z 2 y

Answer: a

Explanation:

fluid-mechanics-questions-answers-geometrical-properties-triangular-section-1-q1

The Area of the Triangle = ½  

Base = Zy+Zy = 2Zy

Area =   

Area = Zy 2 .

2. Calculate the wetted perimeter of a triangular section having depth y and the side slope is Z.

fluid-mechanics-questions-answers-geometrical-properties-triangular-section-1-q2

Answer: d

Explanation: Wetted perimeter = Length of the sides 

fluid-mechanics-questions-answers-geometrical-properties-triangular-section-1-q2a

3. Calculate the wetted perimeter of a triangular section having a depth of 4m and the side slope is1H:1V.

a) 7.94m

b) 8.94m

c) 9.94m

d) 10.94m

Answer: b

Explanation:

fluid-mechanics-questions-answers-geometrical-properties-triangular-section-1-q3

4. Estimate the wetted area of a triangular channel having a depth of 5m and the side slope is 2H:1V.

a) 50m 2

b) 60m 2

c) 70m 2

d) 80m 2

Answer: a

Explanation: Wetted area = Zy 2

= 2(5 2 )

= 50m 2 .

5. What is the top width of a triangular channel having a depth y and side slope Z?

a) Zy

b) Zy 2

c) 2Zy

d) ½Zy

Answer: c

Explanation: Top width = 

= 2Zy.

6. Determine the hydraulic depth of a triangular channel having the side slope Z and depth y.

a) y

b) y/2

c) 2y

d) y 2

Answer: b

Explanation:

fluid-mechanics-questions-answers-geometrical-properties-triangular-section-1-q6

7. Estimate the top width of a triangular channel having a side slope of 1H:2V and depth of 5m.

a) 4m

b) 5m

c) 6m

d) 7m

Answer: b

Explanation: Top Width = 2Zy

Top Width = 

Top Width = 5m.

8. What is the Hydraulic Radius of a triangular channel having a depth y and side slope Z?

fluid-mechanics-questions-answers-geometrical-properties-triangular-section-1-q8

Answer: c

Explanation:

fluid-mechanics-questions-answers-geometrical-properties-triangular-section-1-q8exp

9. What is the section factor for a triangular channel having depth y and side slope Z?

fluid-mechanics-questions-answers-geometrical-properties-triangular-section-1-q9

Answer: c

Explanation:

fluid-mechanics-questions-answers-geometrical-properties-triangular-section-1-q9exp

10. Calculate the section factor a triangular channel section having side slope 1H:4V and depth of 8m.

a) 32

b) 34

c) 36

d) 38

Answer: a

Explanation:

fluid-mechanics-questions-answers-geometrical-properties-triangular-section-1-q10

This set of Advanced Fluid Mechanics Questions and Answers focuses on “Geometrical Properties of Triangular Section – 2”.

1. Determine the Hydraulic depth for a triangular channel having side slope of 1H:3V and depth 15m.

a) 30m

b) 15m

c) 7.5m

d) 3.75m

Answer: c

Explanation: Hydraulic Depth = y/2

= 15/2

= 7.5m.

2. Calculate the Hydraulic Radius for a triangular channel having side slope 2H:4V and a depth of 3m.

a) 0.68m

b) 0.67m

c) 0.66m

d) 0.65m

Answer: b

Explanation:

advanced-fluid-mechanics-questions-answers-q2

3. The Hydraulic Depth of a triangular channel is 5m, calculate the normal depth of the channel.

a) 8m

b) 10m

c) 12m

d) 14m

Answer: b

Explanation: D = y/2

y = 2D = 10m.

4. The hydraulic radius of a triangular section is 0.45m and the normal depth of the channel is 2m, calculate the side slope of the channel.

a) 1/4

b) 1/3

c) 1/2

d) 1

Answer: c

Explanation:

advanced-fluid-mechanics-questions-answers-q4

5. The ratio between hydraulic radius and hydraulic depth of a triangular channel is 31/100, calculate the side slope of the channel.

a) 1⁄2

b) 1⁄3

c) 1⁄4

d) 2⁄3

Answer: b

Explanation:

advanced-fluid-mechanics-questions-answers-q5

6. Calculate the wetted perimeter of a triangular channel section having a depth of 5m and the side slope is equal to tan⁡ 30°.

a) 9.54m

b) 10.54m

c) 11.54m

d) 12.54m

Answer: c

Explanation:

advanced-fluid-mechanics-questions-answers-q6

7. The discharge of water through a triangular section is 90m 3 ⁄s and velocity of flow is 5 m⁄s. Calculate the hydraulic depth of the channel having a side slope 1⁄2.

a) 2m

b) 3m

c) 4m

d) 5m

Answer: b

Explanation:

advanced-fluid-mechanics-questions-answers-q7

8. The top width of a triangular channel section is 4m and the depth of the section is 8m, calculate the wetted perimeter of the channel.

a) 16.5m

b) 17.5m

c) 18.5m

d) 19.5m

Answer: a

Explanation:

advanced-fluid-mechanics-questions-answers-q8

9. In the given figure the vertical angle is 60°, calculate the wetted area of the channel.

advanced-fluid-mechanics-questions-answers-q9

a) 23.3m 2

b) 33.3m 2

c) 43.3m 2

d) 53.3m 2

Answer: c

Explanation: Area = 

Area = 43.3m 2 .

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Geometrical Properties of Trapezoidal Section”.

1. What is the total wetted area of a trapezoidal section of depth y base B and side slope Z?

fluid-mechanics-questions-answers-geometrical-properties-trapezoidal-section-q1

a) Z

b) y

c) Zy 2

d) Zy

Answer: b

Explanation: Total Wetted Area = 2 + 

A = 2( 1 ⁄ 2 Zy) + 

A = Zy 2 + By

A = y.

2. Estimate the wetted perimeter of a trapezoidal section of depth y, base B and side slope Z.

fluid-mechanics-questions-answers-geometrical-properties-trapezoidal-section-q2

Answer: a

Explanation:

fluid-mechanics-questions-answers-geometrical-properties-trapezoidal-section-q2a

3. What is the top width of a trapezoidal channel having depth y, side slope Z and base B?

a) 2Zy

b) Zy

c) B+Zy

d) B+2Zy

Answer: d

Explanation: Top Width = Base+2Zy

T = B+2Zy.

4. Calculate the hydraulic depth of a trapezoidal channel section having depth 4m, base of 5m and side slope 1H:2V.

a) 2.11m

b) 3.11m

c) 4.11m

d) 5.11m

Answer: b

Explanation:

fluid-mechanics-questions-answers-geometrical-properties-trapezoidal-section-q4

5. Calculate the hydraulic radius of a trapezoidal section having depth 5m, side slope 1H:3V and base of 6m.

a) 1.32m

b) 2.08m

c) 1.08m

d) 2.32m

Answer: d

Explanation:

fluid-mechanics-questions-answers-geometrical-properties-trapezoidal-section-q5

6. Calculate the section factor of a trapezoidal channel section having depth 8m, base 5m and side slope 1H:2V.

a) 139.44

b) 149.44

c) 159.44

d) 169.44

Answer: d

Explanation: Section Factor = A√D

fluid-mechanics-questions-answers-geometrical-properties-trapezoidal-section-q6

7. Estimate the discharge of water in a trapezoidal channel section having a depth 3m, width of 6m, side slope of 1H:2V and velocity of water is 2m⁄s.

a) 40m3⁄s

b) 45m3⁄s

c) 50m3⁄s

d) 55m3⁄s

Answer: b

Explanation: Discharge  = AV

A = y

A = )= 22.5m 2

Q = 

Q = 45m3⁄s.

8. Calculate the side slope of a trapezoidal channel section having base 8m, depth 4m and the hydraulic radius is 2.36m.

a) 1⁄6

b) 1⁄3

c) 1⁄2

d) 1⁄4

Answer: c

Explanation: Hydraulic Radius = A/P

fluid-mechanics-questions-answers-geometrical-properties-trapezoidal-section-q8

9. Calculate the top width of a trapezoidal channel section having a side slope1H:4V, base of 5m and the wetted area is 17.25m 2 .

a) 5.5m

b) 6.5m

c) 7.5m

d) 8.5m

Answer: b

Explanation: fluid-mechanics-questions-answers-geometrical-properties-trapezoidal-section-q9

10. The product Zy in a Trapezoidal channel is 2 and the side slope is1/2. Calculate the wetted perimeter of the channel section if the wetted is 32m 2 .

a) 13.94m

b) 14.94m

c) 15.94m

d) 16.94m

Answer: b

Explanation: Zy=2;y=4m

A = y;B=6m

Wetted Perimeter = B+2y√(1+Z 2 )

P = 14.94m.

11. The top width of a trapezoidal channel is 12m, the bottom width of the channel is 6m and the side slope is 1H:2V, calculate the wetted perimeter.

a) 17.41m

b) 18.41m

c) 19.41m

d) 20.41m

Answer: c

Explanation: Top Width = B+2Zy

12 = 6 +2; y=6m

P = B+2y√(1+Z 2 )

P = 19.41m.

12. The wetted area of a trapezoidal section is 15m^2 and the top width is 6m, calculate the section factor.

a) 23.72

b) 24.72

c) 25.72

d) 26.72

Answer: a

Explanation: fluid-mechanics-questions-answers-geometrical-properties-trapezoidal-section-q12

13. The ratio of section factor and hydraulic depth in a trapezoidal section is 324/25, calculate the top width if the total wetted area of the channel is 24m 2 .

a) 4m

b) 5m

c) 6m

d) 7m

Answer: d

Explanation: Ratio = / = 324/25

324/25 =√A √T; √T=49

T = 7m.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Chezy’s Equation”.

1. Calculate the discharge through a channel having a bed slope 1 in 1000, area 12m 2 , hydraulic radius of 1.2m and Chezy’s constant being equal to 50.

a) 17.98 m 3 /s

b) 18.98 m 3 /s

c) 19.98 m 3 /s

d) 20.98 m 3 /s

Answer: d

Explanation:

fluid-mechanics-questions-answers-chezys-equation-q1

2. What is the dimension of C?

a) LT

b) L 1/2 T -1

c) LT -1

d) L -1 T -1

Answer: b

Explanation:

fluid-mechanics-questions-answers-chezys-equation-q2

3. The depth and widths of a rectangular channel are 2m and 5m respectively, calculate the discharge of water through the channel if the bed slope is 1 in 500 and Chezy’s constant being 60.

a) 28.27 m 3 /s

b) 38.27 m 3 /s

c) 48.27 m 3 /s

d) 58.27 m 3 /s

Answer: a

Explanation:

fluid-mechanics-questions-answers-chezys-equation-q3

4. Estimate the discharge of water through a triangular channel having depth 3m, side slope1H:2V, the bed slope is 1 in 500 and C=60.

a) 14.48 m 3 /s

b) 15.48 m 3 /s

c) 16.48 m 3 /s

d) 17.48 m 3 /s

Answer: c

fluid-mechanics-questions-answers-chezys-equation-q4

5. The discharge of water through a trapezoidal channel is 1.5 m 3 /s, the base width of the channel is 7m, the depth is 2m and the side slope is 1H:3V. Bed slope is 1 in 2000, determine the value of the Chezy’s constant.

a) 50

b) 55

c) 60

d) 65

Answer: c

Explanation: fluid-mechanics-questions-answers-chezys-equation-q5

6. Find the discharge through a circular channel section having diameter of 5m, the value of Chezy’s constant is 90 and the bed slope is 1 in 4000.

a) 13.61 m 3 /s

b) 14.61 m 3 /s

c) 15.61 m 3 /s

d) 16.61 m 3 /s

Answer: c

Explanation:

fluid-mechanics-questions-answers-chezys-equation-q6

7. The discharge through a rectangular channel is 16.62 m 3 /s and the wetted area is equal to 12m 2 . The width of the channel is 6m and the bed slope is 1 in 1000, calculate the value of the Chezy’s constant.

a) 35

b) 40

c) 45

d) 50

Answer: b

Explanation:

fluid-mechanics-questions-answers-chezys-equation-q7

8. Calculate the discharge through a triangular channel having a normal depth of 4m, wetted area equalling to 8m 2 and having side slope and bed slopes 1/2 and 1 in 500 respectively. C = 40.

a) 13.54 m 3 /s

b) 14.54 m 3 /s

c) 15.54 m 3 /s

d) 16.54 m 3 /s

Answer: a

Explanation:

fluid-mechanics-questions-answers-chezys-equation-q8

9. The perimeter of a circular channel section is 18.84m, calculate the discharge through the channel when it is running full having a bed slope of 1 in 1500 and C = 60.

a) 53.62 m 3 /s

b) 63.62 m 3 /s

c) 73.62 m 3 /s

d) 83.62 m 3 /s

Answer: a

Explanation:

fluid-mechanics-questions-answers-chezys-equation-q9

10. The discharge through a trapezoidal channel is 61 m 3 /s and the depth and widths of the channel are 4m and 5m respectively. The wetted perimeter of the channel is 13.16m, calculate the bed slope of the channel if the value of C is 45.

a) 1 in 500

b) 1 in 1000

c) 1 in 1500

d) 1 in 2000

Answer: a

Explanation:

fluid-mechanics-questions-answers-chezys-equation-q10

11. The velocity of flow through a channel is 0.74 m/s and the hydraulic radius of the channel is 1.11m, calculate the value of C if the bed slope of the channel is 1 in 5000.

a) 40

b) 45

c) 50

d) 55

Answer: c

Explanation:

fluid-mechanics-questions-answers-chezys-equation-q11

12. Estimate the discharge through a channel having area 24m 2 and perimeter 16m if the bed slope of the channel is equal to 1 in 1000 and C = 70.

a) 62 m 3 /s

b) 63 m 3 /s

c) 64 m 3 /s

d) 65 m 3 /s

Answer: d

Explanation:

fluid-mechanics-questions-answers-chezys-equation-q12

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Manning’s Equation – 1”.

1. A rectangular channel is having depth 2m and width 3m, bed slope of 1 in 700. The value of manning’s roughness co efficient  is 0.06, estimate the discharge through the channel.

a) 2.42m 3 ⁄s

b) 3.42m 3 ⁄s

c) 4.42m 3 ⁄s

d) 5.42m 3 ⁄s

Answer: b

Explanation: fluid-mechanics-questions-answers-mannings-equation-1-q1

2. Estimate the discharge through a triangular channel having depth 7m and side slope 1H:5V in which the bed slope is 1 in 1000. Manning’s co efficient = 0.03.

a) 8.07m 3 ⁄s

b) 9.07m 3 ⁄s

c) 10.07m 3 ⁄s

d) 11.07m 3 ⁄s

Answer: a

Explanation: fluid-mechanics-questions-answers-mannings-equation-1-q2

3. The base width and the depth of a trapezoidal channel is 9m and 5m respectively. Calculate the discharge through a channel if the side slope of the channel is 1H:4V and the bed slope is 1 in 500. 

a) 109.73m 3 ⁄s

b) 110.73m 3 ⁄s

c) 111.73m 3 ⁄s

d) 112.73m 3 ⁄s

Answer: a

Explanation:

fluid-mechanics-questions-answers-mannings-equation-1-q3

4. A circular channel section has diameter of 6m and it is running half. Calculate the discharge through the channel if the bed slope is 1 in 600 and manning’s co efficient is equal to 0.014.

a) 52m 3 ⁄s

b) 53m 3 ⁄s

c) 54m 3 ⁄s

d) 55m 3 ⁄s

Answer: c

Explanation:

fluid-mechanics-questions-answers-mannings-equation-1-q4

5. The diameter of a circular channel section which is running full is 8m. Determine the discharge through the channel section if the bed slope is 1 in 600 and the value of the manning’s co efficient is 0.013.

a) 249.45m 3 ⁄s

b) 250.45m 3 ⁄s

c) 251.45m 3 ⁄s

d) 252.45m 3 ⁄s

Answer: b

Explanation:

fluid-mechanics-questions-answers-mannings-equation-1-q5

6. The area of a channel section is 8m 2 and the wetted perimeter is 8m. Calculate the value of the bed slope of the channel if the discharge is 33.33m 3 ⁄s and manning’s co efficient is 0.012.

a) 1 in 300

b) 1 in 400

c) 1 in 500

d) 1 in 600

Answer: b

Explanation: fluid-mechanics-questions-answers-mannings-equation-1-q6

7. The area of the triangular section is 66.67m 2 and the wetted perimeter of the section is 24.03m. Calculate the value of the manning’s roughness co efficient if the bed slope of the channel section is 1 in 500 and the discharge through the channel is 117.61m 3 ⁄s.

a) 0.03

b) 0.04

c) 0.05

d) 0.06

Answer: c

Explanation: fluid-mechanics-questions-answers-mannings-equation-1-q7

8. The discharge through a trapezoidal channel is 245.06m 3 ⁄s and the bed slope is 1 in 1000. Calculate the value of the wetted area if the hydraulic radius is 2.26m. Manning’s roughness co efficient = 0.008.

a) 34m 2

b) 35m 2

c) 36m 2

d) 37m 2

Answer: c

Explanation:

fluid-mechanics-questions-answers-mannings-equation-1-q8

9. Determine the value of manning’s constant for a rectangular channel if Chezy’s constant is equal to 50 and the depth and widths of the channel are 4m and 7m respectively.

a) 0.012

b) 0.022

c) 0.032

d) 0.042

Answer: b

Explanation: fluid-mechanics-questions-answers-mannings-equation-1-q9

10. The side slope of a triangular channel section is 1H:4V and the depth is 12m. Calculate the value of chezy’s constant if the value of manning’s constant is 0.03.

a) 32.48

b) 33.48

c) 34.48

d) 35.48

Answer: d

Explanation: fluid-mechanics-questions-answers-mannings-equation-1-q10

11. Determine the value of Chezy’ s constant for a trapezoidal channel having depth 3m, base width 11m, side slope 1H:3V and the manning’s co efficient is 0.012.

a) 94.15

b) 94.25

c) 94.35

d) 94.45

Answer: a

Explanation:

fluid-mechanics-questions-answers-mannings-equation-1-q11

12. Estimate the value of the manning’s constant for a fully running circular section having diameter of 8m and the value of Chezy’s constant is 50.

a) 0.022

b) 0.032

c) 0.042

d) 0.052

Answer: a

Explanation:

fluid-mechanics-questions-answers-mannings-equation-1-q12

This set of Tricky Fluid Mechanics Questions and Answers focuses on “Manning’s Equation – 2”.

1. The area of a circular section which is running half full is 19.625m 2 and the value of the chezy’s constant is 60.

a) 0.019

b) 0.020

c) 0.021

d) 0.022

Answer: a

Explanation: tricky-fluid-mechanics-questions-answers-q1

2. A circular section which is  th full is having a wetted perimeter of 9.42m. Calculate the value of C if n is equal to 0.025.

a) 30

b) 40

c) 50

d) 60

Answer: b

Explanation:

tricky-fluid-mechanics-questions-answers-q2

3. The dimensions of a rectangular channel section are 3m in width and 1m in depth. Calculate the average shear stress if the bed slope of the channel is 1 in 500.

a) 9.772 N/m 2

b) 10.772N/m 2

c) 11.772N/m 2

d) 12.772N/m 2

Answer: c

Explanation:

tricky-fluid-mechanics-questions-answers-q3

4. Calculate the bed slope of a triangular channel having depth 12m and side slope of 1H:6V if the average shear stress is 9.6138 N/m 2 .

a) 1 in 500

b) 1 in 1000

c) 1 in 1500

d) 1 in 2000

Answer: b

Explanation:

tricky-fluid-mechanics-questions-answers-q4

5. The average shear stress for a circular channel running full is 32.7N⁄m 2 and the diameter of the channel is 8m then calculate the bed slope of the channel.

a) 1 in 500

b) 1 in 600

c) 1 in 700

d) 1 in 800

Answer: b

Explanation:

tricky-fluid-mechanics-questions-answers-q5

6. Determine the average shear stress of a trapezoidal channel having base width 6m, depth 5m and side slope 1H:3V if the bed slope of the channel is 1 in 700.

a) 28.45N/m 2

b) 38.45N/m 2

c) 48.45N/m 2

d) 58.45N/m 2

Answer: a

Explanation:

tricky-fluid-mechanics-questions-answers-q6

7. Estimate the value of Chezy’s constant if the value of the friction factor is 0.031.

a) 35

b) 40

c) 45

d) 50

Answer: d

Explanation:

tricky-fluid-mechanics-questions-answers-q7

8. Calculate the average shear stress if the friction factor is 0.28 and velocity of flow is 1.5m⁄s.

a) 60N/m 2

b) 70N/m 2

c) 80N/m 2

d) 90N/m 2

Answer: c

Explanation:

tricky-fluid-mechanics-questions-answers-q8

9. Calculate the conveyance of a rectangular channel having depth 0.5m and width 0.8m. C = 50.

a) 6.42m 3 ⁄s

b) 7.42m 3 ⁄s

c) 8.42m 3 ⁄s

d) 9.42m 3 ⁄s

Answer: d

Explanation: Conveyance  = AC√R

A = By = 0.4m 2

P = B+2y = 1.8m

R = 0.22m

K = 0.4√0.22

K = 9.42 m 3 /s.

10. Determine the conveyance of a trapezoidal channel having depth 3m, width 9m, side slope 1H:2V and the manning’s co efficient is 0.03.

a) 864.79m 3 /s

b) 865.79m 3 /s

c) 866.79m 3 /s

d) 867.79m 3 /s

Answer: b

Explanation:

tricky-fluid-mechanics-questions-answers-q10

11. Determine the conveyance of a triangular section having area 30m^2 and perimeter 15m. 

a) 1695m 3 /s

b) 1696m 3 /s

c) 1697m 3 /s

d) 1698m 3 /s

Answer: c

Explanation: tricky-fluid-mechanics-questions-answers-q11

12. Estimate the conveyance of a circular channel of diameter 0.7m having manning’s co efficient equal to 0.012.

a) 6.83m 3 /s

b) 7.83m 3 /s

c) 8.83m 3 /s

d) 9.83m 3 /s

Answer: d

Explanation:

tricky-fluid-mechanics-questions-answers-q12

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Most Economic Rectangular Section”.

1. For a channel to be economic which of the following parameters should be minimum.

a) Wetted perimeter

b) Wetted area

c) Section factor

d) Hydraulic depth

Answer: a

Explanation: If the wetted perimeter is minimum, amount of materials required for construction of the channel is less and hence the channel is more economical.

2. A rectangular channel section has depth y and width B, calculate the most economical area of the channel.

a) 2y 2

b) y 2

c) By

d) B 2

Answer: a

Explanation: fluid-mechanics-questions-answers-most-economic-rectangular-section-q2

3. The depth and widths of a rectangular channel section are y and B respectively, determine the economical perimeter of the section.

a) y

b) 2y

c) 3y

d) 4y

Answer: d

Explanation:

fluid-mechanics-questions-answers-most-economic-rectangular-section-q3

4. Calculate the hydraulic radius for the most economical rectangular section having depth y and width B.

a) y/2

b) y

c) 2y

d) 3y

Answer: a

Explanation:

fluid-mechanics-questions-answers-most-economic-rectangular-section-q4

5. Calculate the maximum discharge through a rectangular channel having depth 3m, bed slope of 1 in 1000.

a) 33.85m 3 /s

b) 34.85m 3 /s

c) 35.85m 3 /s

d) 36.85m 3 /s

Answer: b

Explanation:

fluid-mechanics-questions-answers-most-economic-rectangular-section-q5

6. Calculate the maximum discharge through a rectangular channel having width of 5m, bed slope of 1 in 500 and manning’s co efficient is 0.020.

a) 33.43m 3 ⁄s

b) 32.43m 3 ⁄s

c) 31.43m 3 ⁄s

d) 30.43m 3 ⁄s

Answer: b

Explanation:

fluid-mechanics-questions-answers-most-economic-rectangular-section-q6

7. The maximum discharge through a rectangular channel is 7.15m 3 ⁄s, determine the depth of the channel where S 0 = 1/2000 and C=40.

a) 4m

b) 3m

c) 2m

d) 1m

Answer: c

Explanation: fluid-mechanics-questions-answers-most-economic-rectangular-section-q7

8. The base width of a most economical rectangular channel is 8m, calculate the hydraulic radius of the channel,

a) 5m

b) 4m

c) 3m

d) 2m

Answer: d

Explanation: B = 2y; y = 4m

R = y/2 = 2m.

9. Calculate the section factor for the most economical rectangular section having depth of 4m.

a) 32

b) 64

c) 128

d) 256

Answer: b

Explanation: Z = A√D = 2y 2 √y = 2y 5/2

Z = 64.

10. The ratio between maximum discharge and top width of a rectangular channel is 91:50, calculate the depth of the channel if the bed slope is 1 in 3000 and C = 50.

a) 2m

b) 3m

c) 4m

d) 5m

Answer: a

Explanation:

fluid-mechanics-questions-answers-most-economic-rectangular-section-q10

11. The ratio between normal discharge and maximum discharge through a rectangular channel is 32:6, calculate the depth of the channel if the width of the channel is 4m and bed slope, chezy’s constant remains same.

a) 1m

b) 2m

c) 3m

d) 4m

Answer: a

Explanation:

fluid-mechanics-questions-answers-most-economic-rectangular-section-q11

12. The hydraulic radius of an economical rectangular section is 4m, calculate the discharge through the channel if the bed slope of the channel is 1 in 1000 and manning’s co efficient is 0.015.

a) 680m 3 ⁄s

b) 690m 3 ⁄s

c) 700m 3 ⁄s

d) 710 m 3 ⁄s

Answer: a

Explanation:

fluid-mechanics-questions-answers-most-economic-rectangular-section-q12

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Most Economic Trapezoidal Section”.

1. Determine the top width length of the most economical trapezoidal channel section having depth y and side slope Z.

fluid-mechanics-questions-answers-most-economic-trapezoidal-section-q1

Answer: d

Explanation: fluid-mechanics-questions-answers-most-economic-trapezoidal-section-q1a

2. Estimate the hydraulic radius of the most economical trapezoidal channel section having depth y and side slope Z.

a) y ⁄ 2

b) y

c) 2y

d) 3y

Answer: a

Explanation:

fluid-mechanics-questions-answers-most-economic-trapezoidal-section-q2

3. The top width of a most economical trapezoidal channel section is 7m and the side slope of the channel is 1H:2V, determine the depth of the channel section.

a) 2.13m

b) 3.13m

c) 4.13m

d) 5.13m

Answer: b

Explanation:

fluid-mechanics-questions-answers-most-economic-trapezoidal-section-q3

4. The top width of a most economical trapezoidal channel section is 8m, determine the hydraulic radius of the channel if the side slope is 1H:3V.

a) 1.8m

b) 1.9m

c) 2.0m

d) 2.1m

Answer: b

Explanation:

fluid-mechanics-questions-answers-most-economic-trapezoidal-section-q4

5. The base of the most economical trapezoidal channel section is 6m and the side slope is 1H:2V, calculate the maximum discharge through the channel if the bed slope is 1 in 1000 and C = 50.

a) 120.61 m 3 /s

b) 110.61 m 3 /s

c) 100.61 m 3 /s

d) 90.61 m 3 /s

Answer: c

Explanation:

fluid-mechanics-questions-answers-most-economic-trapezoidal-section-q5

6. Calculate the maximum discharge through a trapezoidal section having depth 3m, side slope 1H:4V and bed slope of 1 in 2000. Given: n = 0.025.

a) 19.09 m 3 /s

b) 20.09 m 3 /s

c) 21.09 m 3 /s

d) 22.09 m 3 /s

Answer: a

Explanation: fluid-mechanics-questions-answers-most-economic-trapezoidal-section-q6

7. The wetted area of a most economical trapezoidal section is 21.58m 2 , base width of 5m and side slope of 1H:3V. Calculate the maximum discharge through the channel if the C=60 and S 0 =1/500.

a) 56.32 m 3 / s

b) 66.32 m 3 / s

c) 76.32 m 3 / s

d) 86.32 m 3 / s

Answer: c

Explanation:

fluid-mechanics-questions-answers-most-economic-trapezoidal-section-q7

8. Calculate the depth of the most economical trapezoidal channel section having wetted area equal to 50m 2 and the side slope of 1H:5V.

a) 3.21m

b) 4.21m

c) 5.21m

d) 6.21m

Answer: c

Explanation: fluid-mechanics-questions-answers-most-economic-trapezoidal-section-q8

9. The wetted perimeter of the most economical trapezoidal section is 7.47m, the base width is 3m and has the side slope of 1H:2V.

a) 1m

b) 2m

c) 3m

d) 4m

Answer: b

Explanation:

fluid-mechanics-questions-answers-most-economic-trapezoidal-section-q9

10. Calculate the maximum discharge through a trapezoidal channel if the wetted perimeter is 6.24m, side slope of 1H:2V and base width of 4m. Given: C=55 and S 0 =1/1500.

a) 3.52 m 3 /s

b) 4.52 m 3 /s

c) 5.52 m 3 /s

d) 6.52 m 3 /s

Answer: b

Explanation: fluid-mechanics-questions-answers-most-economic-trapezoidal-section-q10

11. The maximum discharge through the trapezoidal channel is 20 m 3 /s and the velocity of flow is 5 m/s. Calculate the base width of the channel if the side slope is 1H:4V.

a) 3.31m

b) 2.31m

c) 1.31m

d) 0.31m

Answer: b

Explanation: fluid-mechanics-questions-answers-most-economic-trapezoidal-section-q11

12. What is the side slope for the most economic trapezoidal channel having depth y and base width B?

fluid-mechanics-questions-answers-most-economic-trapezoidal-section-q12a

Answer: b

Explanation: fluid-mechanics-questions-answers-most-economic-trapezoidal-section-q12

13. What is the angle made by the sloping side when the trapezoidal channel discharges to the maximum extent?

a) 30°

b) 45°

c) 60°

d) 90°

Answer: c

Explanation:

fluid-mechanics-questions-answers-most-economic-trapezoidal-section-q13

14. Calculate the maximum discharge through a trapezoidal channel if the depth is 5m.

a) 56.67 m 3 /s

b) 66.67 m 3 /s

c) 76.67 m 3 /s

d) 86.67 m 3 /s

Answer: d

Explanation: fluid-mechanics-questions-answers-most-economic-trapezoidal-section-q14

15. If the side slope angle in a trapezoidal section is 45° and it discharges to the maximize extent, calculate the top width of the channel section. Given: y = 4m

a) 10.31m

b) 11.31m

c) 12.31m

d) 13.31m

Answer: b

Explanation:

fluid-mechanics-questions-answers-most-economic-trapezoidal-section-q15

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Most Economic Circular Section – 1”.

1. Estimate the wetted perimeter of a circular channel having radius R and depth d, if the angle subtended at the centre is Ɵ.

a) RƟ ⁄ 2

b) RƟ

c) 2RƟ

d) 3RƟ

Answer: c

Explanation: fluid-mechanics-questions-answers-most-economic-circular-section-1-q1

Wetted Perimeter = Arc ABC

P = RƟ.

2. Calculate the wetted area of a circular channel having depth d and radius R.

fluid-mechanics-questions-answers-most-economic-circular-section-1-q2

Answer: a

Explanation:

fluid-mechanics-questions-answers-most-economic-circular-section-1-q2a

3. Determine the hydraulic radius of a circular section having depth d and radius R.

fluid-mechanics-questions-answers-most-economic-circular-section-1-q3

Answer: a

Explanation:

fluid-mechanics-questions-answers-most-economic-circular-section-1-q3a

4. A circular channel section has water at a depth of 2m and the radius of the section is 4m, calculate the wetted area of the channel.

a) 6.87m 2

b) 7.87m 2

c) 8.87m 2

d) 9.87m 2

Answer: d

Explanation: fluid-mechanics-questions-answers-most-economic-circular-section-1-q4

5. Calculate the wetted perimeter of a circular channel if the depth of water is 2m and radius is 5m.

a) 9.27m

b) 10.27m

c) 11.27m

d) 12.27m

Answer: a

Explanation:

fluid-mechanics-questions-answers-most-economic-circular-section-1-q5

6. Calculate the hydraulic radius of a circular channel having depth 6m and radius 4m.

a) 0.41m

b) 1.41m

c) 2.41m

d) 3.41m

Answer: c

Explanation:

fluid-mechanics-questions-answers-most-economic-circular-section-1-q6

7. Calculate the discharge through a circular channel section if the depth is 5m, radius of the circular section is 3m and the bed slope is 1 in 1000. Given: C = 50.

a) 25.74 m 3 /s

b) 26.74 m 3 /s

c) 27.74 m 3 /s

d) 28.74 m 3 /s

Answer: c

Explanation:

fluid-mechanics-questions-answers-most-economic-circular-section-1-q7

8. Estimate the discharge through a circular channel section having radius 4m and depth 3m if the channel bed slope is 1 in 2000. Given: n = 0.015.

a) 15.8 m 3 /s

b) 16.8 m 3 /s

c) 17.8 m 3 /s

d) 18.8 m 3 /s

Answer: c

Explanation:

fluid-mechanics-questions-answers-most-economic-circular-section-1-q8

9. Calculate the hydraulic radius of a circular channel if the radius is 6m and the central angle is 70°.

a) 0.58m

b) 0.68m

c) 0.78m

d) 0.88m

Answer: b

Explanation: fluid-mechanics-questions-answers-most-economic-circular-section-1-q9

10. The hydraulic radius of a circular channel section is 0.33m, calculate the radius of the channel if the central angle is 60°.

a) 2m

b) 3m

c) 4m

d) 5m

Answer: c

Explanation: fluid-mechanics-questions-answers-most-economic-circular-section-1-q10

11. The discharge through a circular channel section is 14.67m 3 /s and the velocity of flow is 1.47m/s, calculate the radius of the section if Ɵ = 75°.

a) 2m

b) 3m

c) 4m

d) 5m

Answer: d

Explanation: fluid-mechanics-questions-answers-most-economic-circular-section-1-q11

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Most Economic Circular Section – 2”.

1. Estimate the hydraulic depth for a most economical circular channel section in case of maximum velocity.

a) 0.2D

b) 0.3D

c) 0.4D

d) 0.5D

Answer: b

Explanation: fluid-mechanics-questions-answers-most-economic-circular-section-2-q1

2. What is the value of θ in a most economical circular section in case of maximum discharge?

a) 150°

b) 152°

c) 154°

d) 156°

Answer: c

Explanation: The equation in case for maximum discharge is,

4Ɵ – 6θ cos⁡ 2θ + sin ⁡2θ = 0 where θ = 154°.

3. Calculate the depth in a most economical circular section in case of maximum discharge.

a) 0.65D

b) 0.75D

c) 0.85D

d) 0.95D

Answer: d

Answer: d

Explanation:

fluid-mechanics-questions-answers-most-economic-circular-section-2-q3

4. Calculate the hydraulic radius of a circular channel in case of maximum discharge if the radius of the channel is 4m.

a) 1.7m

b) 2.0m

c) 2.3m

d) 2.6m

Answer: c

Explanation:

fluid-mechanics-questions-answers-most-economic-circular-section-2-q4

5. Calculate the wetted area of a circular channel section in case of maximum velocity.

a) 5.47m 2

b) 6.47m 2

c) 7.47m 2

d) 8.47m 2

Answer: a

Explanation:

fluid-mechanics-questions-answers-most-economic-circular-section-2-q5

6. Calculate the wetted perimeter of the most economical circular section having radius 3m in case of maximum discharge.

a) 15.12m

b) 16.12m

c) 17.12m

d) 18.12m

Answer: b

Explanation: P = 2Rθ = 2 = 16.12m.

7. What is the value of wetted perimeter of a circular section having radius 6m in case of maximum velocity?

a) 12.47m

b) 13.47m

c) 14.47m

d) 15.47m

Answer: b

Explanation: P = 2Rθ = 2 = 13.47m.

8. Estimate the value of wetted area of a circular section in case of maximum discharge if the radius of the channel is 7m.

a) 134m 2

b) 144m 2

c) 154m 2

d) 164m 2

Answer: a

Explanation:

fluid-mechanics-questions-answers-most-economic-circular-section-2-q8

9. Calculate the hydraulic radius in case of maximum velocity if the radius of the section is 8m.

a) 7.87m

b) 6.87m

c) 5.87m

d) 4.87m

Answer: d

Explanation:

fluid-mechanics-questions-answers-most-economic-circular-section-2-q9

10. Calculate the discharge through a most economical circular section in case of maximum velocity if the radius of the channel is 0.5m, bed slope of 1 in 500 and the value of n = 0.016.

a) 0.43 m 3 /s

b) 0.53 m 3 /s

c) 0.63 m 3 /s

d) 0.73 m 3 /s

Answer: a

Explanation: fluid-mechanics-questions-answers-most-economic-circular-section-2-q10

This set of Tough Fluid Mechanics Questions and Answers focuses on “Most Economic Circular Section – 3”.

1. Which of the following conditions is taken into account in case of most economical circular channel section?

a) Minimum wetted perimeter

b) Minimum wetted area

c) Maximum velocity

d) Maximum depth

Answer: c

Explanation: In case of a circular channel the depth continuously varies, hence the wetted area and wetted perimeter changes. Therefore the condition of maximum velocity is taken under consideration.

2. What is the condition for maximum velocity in case of most economical circular section?

a) sin⁡ 2θ=2θ

b) cos⁡ 2θ=2θ

c) tan⁡ 2θ=2θ

d) sec⁡ 2θ=2θ

Answer: c

Explanation:

tough-fluid-mechanics-questions-answers-q2

3. What is the value of the θ in case of most economical circular channel section?

a) 128°45′

b) 129°45′

c) 130°45′

d) 131°45′

Answer: a

Explanation: tan⁡ 2θ=2θ where θ= 128°45.

4. What is the depth of flow in case most economical circular section considering maximum velocity?

a) 0.61D

b) 0.71D

c) 0.81D

d) 0.91D

Answer: c

Explanation:

tough-fluid-mechanics-questions-answers-q4

5. Determine the depth of flow in case of maximum velocity when the radius of the channel is 2.2m.

a) 3.56m

b) 4.56m

c) 5.56m

d) 6.56m

Answer: a

Explanation: Depth = 0.81D = 0.81 = 3.56m.

6. The maximum discharge through a most economical circular section in case of maximum velocity is 0.16 m 3 /s calculate the bed slope of the channel if the radius is 0.4m and C = 55.

a) 1 in 1000

b) 1 in 1100

c) 1 in 1200

d) 1 in 1300

Answer: c

Explanation: tough-fluid-mechanics-questions-answers-q6

7. The maximum discharge through a circular channel is 0.38 m 3 /s and the radius of the channel is 0.6m. Calculate the value of C if S 0 =1 in 1000.

a) 45

b) 50

c) 55

d) 60

Answer: b

Explanation: tough-fluid-mechanics-questions-answers-q7

8. The maximum discharge through a circular channel is 0.61 m 3 /s and the radius of the section is 0.7m. Calculate the value of n if the bed slope value is 1 in 1100.

a) 0.018

b) 0.019

c) 0.020

d) 0.021

Answer: c

Explanation: tough-fluid-mechanics-questions-answers-q8

9. Calculate the hydraulic mean depth in case of maximum mean velocity if the radius of the channel is 0.5m.

a) 0.3m

b) 0.4m

c) 0.5m

d) 0.6m

Answer: a

Explanation: R = 0.3D = 0.3 = 0.3m.

10. Calculate the depth in case of circular channel discharging to the maximum extent if the radius of the channel is 2m.

a) 1.8m

b) 2.8m

c) 3.8m

d) 4.8m

Answer: c

Explanation: Depth = 0.95D = 0.95 = 3.8m.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Specific Energy – 1”.

1. What is energy per unit head of water called as __________

a) Total energy

b) Specific energy

c) Velocity head

d) Datum head

Answer: a

Explanation: Total Energy = Pressure head + Velocity head + Datum head

Hence energy per unit head is called as total energy.

2. What is the plot between Total energy and channel position called as?

a) Specific grade line

b) Energy grade line

c) Datum line

d) Velocity line

Answer: b

Explanation: The graph between total energy and channel position gives the distribution of energy along the channel and hence the plot is called energy grade line.

3. Which of the following conditions is not true for an uniform flow?

a) y 1 = y 2

b) S 0 = S f

c) Z 1 = Z 2

d) V 1 = V 2

Answer: c

Explanation: In a uniform flow through a channel the depth, slopes and the velocity of flow remains constant throughout the channel but the datum head may or may not be the same.

4. Energy per unit weight of water measured with respect to the datum is called as _______

a) Total energy

b) Specific energy

c) Velocity head

d) Datum head

Answer: b

Explanation: Specific energy is the energy constant throughout the channel and is estimated with respect to the datum.

5. For a given discharge Q and area A, specific energy is constant.

a) True

b) False

Answer: a

Explanation: Specific energy is constant throughout the channel and is given by

fluid-mechanics-questions-answers-specific-energy-1-q5

and hence for a given Q and A, E is constant.

6. Calculate the specific energy for a channel having depth 3m and velocity of flow being 1.5 m/s

a) 2.11m

b) 3.11m

c) 4.11m

d) 5.11m

Answer: b

Explanation:

fluid-mechanics-questions-answers-specific-energy-1-q6

7. Calculate the specific energy for a rectangular channel having depth 2m and width 3m. Given: Discharge  = 8.78 m 3 /s.

a) 2.11m

b) 3.11m

c) 4.11m

d) 5.11m

Answer: a

Explanation: fluid-mechanics-questions-answers-specific-energy-1-q7

8. Calculate the specific energy for a triangular channel having depth 4m, side slope 1H:2V and bed slope of 1 in 1000. Given: C = 40.

a) 2.07m

b) 3.07m

c) 4.07m

d) 5.07m

Answer: c

Explanation:

fluid-mechanics-questions-answers-specific-energy-1-q8

9. Calculate the specific energy of a trapezoidal channel having depth 2m, base width of 5m and side slope of 1H:2V. Given : S 0 = 1/1000 and C = 50.

a) 2.16m

b) 3.16m

c) 4.16m

d) 5.16m

Answer: a

Explanation:

fluid-mechanics-questions-answers-specific-energy-1-q9

10. A circular channel has diameter of 6m, calculate the specific energy of the channel if the bed slope of the channel is 1 in 1000. Given: C = 60.

a) 5.27m

b) 6.27m

c) 7.27m

d) 8.27m

Answer: b

Explanation:

fluid-mechanics-questions-answers-specific-energy-1-q10

11. The specific energy of a triangular channel is 5.06m and the depth of the channel is 5m having side slope of 1H:4V then calculate the value of C. Given: S 0 =1 in 1000.

a) 40

b) 45

c) 50

d) 55

Answer: b

Explanation:

fluid-mechanics-questions-answers-specific-energy-1-q11

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Specific Energy – 2”.

1. The dimensions of a rectangular channel are 3m in depth and 4m in width. Calculate the bed slope of the channel if the specific energy is 3.13m. [C=50]

a) 1 in 1000

b) 1 in 1100

c) 1 in 1200

d) 1 in 1300

Answer: c

Explanation:

fluid-mechanics-questions-answers-specific-energy-2-q1

2. The depth of a trapezoidal channel section is 2m, base width of 3m and has a side slope of 1H:2V. Calculate n if the bed slope is 1 in 1000.

a) 0.012

b) 0.013

c) 0.014

d) 0.015

Answer: b

Explanation:

fluid-mechanics-questions-answers-specific-energy-2-q2

3. The specific energy of a channel section is 1.01m and the velocity of flow is 0.5m⁄s, calculate the depth of flow.

a) 0.8m

b) 1.0m

c) 1.2m

d) 1.4m

Answer: b

Explanation: fluid-mechanics-questions-answers-specific-energy-2-q3

4. Calculate the velocity of flow through a channel having depth of 1.2m and specific energy equal to 1.24m.

a) 0.6 m/s

b) 0.7 m/s

c) 0.8m/s

d) 0.9m/s

Answer: d

Explanation: fluid-mechanics-questions-answers-specific-energy-2-q4

5. What is the equation of the curve AB?

fluid-mechanics-questions-answers-specific-energy-2-q5

fluid-mechanics-questions-answers-specific-energy-2-q5a

Answer: d

Explanation: The curve AB  is the combination of a parabola and a straight line, hence the valid equation is

fluid-mechanics-questions-answers-specific-energy-2-q5exp

6. What are y1 and y2 in the adjoining graph?

fluid-mechanics-questions-answers-specific-energy-2-q6

a) Conjugate depths

b) Alternate depths

c) Equal depths

d) Sequent depths

Answer: b

Explanation: For a particular specific energy above the minimum specific energy there are two depths called as alternate depths.

7. The specific energy of a rectangular channel having dimensions 2m×3m is 3.095m. Calculate the friction factor.

a) 0.01

b) 0.02

c) 0.03

d) 0.04

Answer: c

Explanation:

fluid-mechanics-questions-answers-specific-energy-2-q7

8. Calculate the average shear stress for a rectangular channel having depth 0.5m, width 0.8m if the specific energy is 0.56m.

a) 2.32 N/m 2

b) 3.32 N/m 2

c) 4.32 N/m 2

d) 5.32 N/m 2

Answer: c

Explanation:

fluid-mechanics-questions-answers-specific-energy-2-q8

9. Calculate the specific energy for the most economical rectangular channel having depth 2m and width 4m if the bed slope of the channel is 1 in 1200. C = 35.

a) 2.05m

b) 3.05m

c) 4.05m

d) 5.05m

Answer: a

Explanation: fluid-mechanics-questions-answers-specific-energy-2-q9

10. Estimate the specific energy for the most economical trapezoidal channel section having depth of 5m, side slope of 1H:4V and bed slope of 1 in 1200.

a) 1.14m

b) 2.14m

c) 3.14m

d) 4.14m

Answer: b

Explanation: fluid-mechanics-questions-answers-specific-energy-2-q10

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Critical Flow in Different Channel Sections – 1”.

1. What is the condition for critical flow?

fluid-mechanics-questions-answers-critical-flow-different-channel-sections-1-q1

Answer: d

Explanation:

fluid-mechanics-questions-answers-critical-flow-different-channel-sections-1-q1a

2. What is the condition for critical flow in case of maximum discharge?

fluid-mechanics-questions-answers-critical-flow-different-channel-sections-1-q1

Answer: d

Explanation: fluid-mechanics-questions-answers-critical-flow-different-channel-sections-1-q2

3. Determine the velocity in case of critical flow having top width T and area A.

fluid-mechanics-questions-answers-critical-flow-different-channel-sections-1-q3

Answer: b

Explanation: fluid-mechanics-questions-answers-critical-flow-different-channel-sections-1-q3a

4. Calculate the specific energy in case of rectangular channel having discharge Q and y c is the critical depth

fluid-mechanics-questions-answers-critical-flow-different-channel-sections-1-q4

Answer: b

Explanation:

fluid-mechanics-questions-answers-critical-flow-different-channel-sections-1-q4a

5. Estimate the critical depth in case of a rectangular channel having usual dimensions.

fluid-mechanics-questions-answers-critical-flow-different-channel-sections-1-q5

Answer: b

Explanation:

fluid-mechanics-questions-answers-critical-flow-different-channel-sections-1-q5a

6. Calculate the critical depth of a rectangular channel having width 3m and the discharge through it is 15 m 3 /s.

a) 0.36m

b) 1.36m

c) 2.36m

d) 3.36m

Answer: b

Explanation:

fluid-mechanics-questions-answers-critical-flow-different-channel-sections-1-q6

7. Calculate the total discharge through a rectangular channel having critical depth of 1.18m and the base width of the channel is 4m.

a) 16 m 3 /s

b) 20 m 3 /s

c) 24 m 3 /s

d) 28 m 3 /s

Answer: a

Explanation:

fluid-mechanics-questions-answers-critical-flow-different-channel-sections-1-q7

8. Calculate the minimum specific energy of a rectangular channel having critical depth of 1.5m.

a) 3.25m

b) 2.25m

c) 1.25m

d) 0.25m

Answer: b

Explanation: Minimum specific energy E c = 3 ⁄ 2 y c = 2.25m.

9. The base width of a rectangular channel is 4m and the maximum discharge through the channel is 10 m3/s, calculate the specific energy.

a) 0.7m

b) 1.0m

c) 1.3m

d) 1.6m

Answer: c

Explanation: fluid-mechanics-questions-answers-critical-flow-different-channel-sections-1-q9

10. The minimum specific energy of a rectangular channel is 1.3m and the base width of the channel is 10m, calculate the discharge through the channel.

a) 10 m 3 /s

b) 15 m 3 /s

c) 20m 3 /s

d) 25m 3 /s

Answer: d

Explanation: fluid-mechanics-questions-answers-critical-flow-different-channel-sections-1-q10

This set of Fluid Mechanics Questions & Answers for Exams focuses on “Critical Flow in Different Channel Sections – 2”.

1. Calculate the maximum discharge through a triangular channel having a side slope of 1H:2V and the critical depth is 3m.

a) 15.26 m 3 /s

b) 16.26 m 3 /s

c) 17.26 m 3 /s

d) 18.26 m 3 /s

Answer: c

Explanation: fluid-mechanics-exam-questions-answers-q1

2. Calculate the side slope of a triangular channel if the maximum discharge is 48.82 m3/s and the critical depth of the channel is 6m.

a) 1H:2V

b) 1H:3V

c) 1H:4V

d) 1H:5V

Answer: c

Explanation:

fluid-mechanics-exam-questions-answers-q2

3. The critical depth and base width of a trapezoidal channel is 2m and 5m respectively. Calculate the maximum discharge if the side slope of the channel is 1H:2V.

a) 29.21 m 3 /s

b) 39.21 m 3 /s

c) 49.21 m 3 /s

d) 50.21 m 3 /s

Answer: c

Explanation:

fluid-mechanics-exam-questions-answers-q3

4. The maximum discharge through a trapezoidal channel is 74.28 m 3 /s. Calculate the critical depth of the channel is the side slope is equal to 1H:3V. B = 5m.

a) 2m

b) 3m

c) 4m

d) 5m

Answer: b

Explanation:

fluid-mechanics-exam-questions-answers-q4

5. For a critical flow Froude’s number is equal to 1.

a) True

b) False

Answer: a

Explanation: fluid-mechanics-exam-questions-answers-q5

6. Calculate Froude’s number for a rectangular channel having depth 5m and velocity of flow is 5.94 m/s.

a) 1.0

b) 1.2

c) 1.4

d) 1.6

Answer: b

Explanation:

fluid-mechanics-exam-questions-answers-q6

7. Calculate the value of F r if the value of hydraulic depth is 0.56m and the velocity of flow is 2.5 m/s.

a) 1.0

b) 1.5

c) 2.0

d) 2.5

Answer: b

Explanation:

fluid-mechanics-exam-questions-answers-q7

8. Calculate the Froude’s number for a triangular channel having depth 4m and side slope of 1H:4V. V = 1m/s.

a) 0.52

b) 0.42

c) 0.32

d) 0.22

Answer: d

Explanation:

fluid-mechanics-exam-questions-answers-q8

9. The top width of a triangular channel is 6m and the side slope of the channel is 1H:3V. Calculate the velocity of flow.

a) 5.54 m/s

b) 6.64 m/s

c) 7.64 m/s

d) 8.64 m/s

Answer: b

Explanation:

fluid-mechanics-exam-questions-answers-q9

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Gradually Varied Flow – 1”.

1. Which of the following assumptions about a GVF is false?

a) Channel is prismatic

b) Pressure distribution is hydrostatic

c) Flow characteristics change with time

d) Roughness co efficient is constant

Answer: c

Explanation: In a GVF, the flow is steady and hence the flow characteristics does not change with time.

2. Calculate the total discharge though a rectangular channel having depth 2m and width 4m if the value of C = 50 and if the slope of the energy line is 0.00004.

a) 1.53 m 3 /s

b) 2.53 m 3 /s

c) 3.53 m 3 /s

d) 4.53 m 3 /s

Answer: b

Explanation:

fluid-mechanics-questions-answers-gradually-varied-flow-gvf-1-q2

3. Calculate S f for a triangular channel if the depth of the channel is 5m and the side slope is 1H:2V. Given: Q = 5.80 m 3 /s , C = 40.

a) 0.00010

b) 0.00011

c) 0.00012

d) 0.00013

Answer: c

Explanation:

fluid-mechanics-questions-answers-gradually-varied-flow-gvf-1-q3

4. Calculate the discharge through a trapezoidal channel section if the depth of the channel is 3m and the base width is 3m. Given: C = 30, S f = 0.0005, A = 12m 2 .

a) 6.10 m 3 /s

b) 7.10 m 3 /s

c) 8.10 m 3 /s

d) 9.10 m 3 /s

Answer: d

Explanation:

fluid-mechanics-questions-answers-gradually-varied-flow-gvf-1-q4

5. The discharge through a circular channel section having diameter 4m which is running half is 4.35 m 3 /s and the value of slope of energy line is S f = 0.0003, calculate the value of C.

a) 50

b) 45

c) 40

d) 35

Answer: c

Explanation:

fluid-mechanics-questions-answers-gradually-varied-flow-gvf-1-q5

6. Determine the dynamic equation for the rate of change of depth having bed slope S 0 and slope of total energy line S f .

fluid-mechanics-questions-answers-gradually-varied-flow-gvf-1-q6

Answer: c

Explanation: fluid-mechanics-questions-answers-gradually-varied-flow-gvf-1-q6a

7. Determine the dynamic equation for the rate of change of depth having bed slope S 0 and slope of total energy line S f in terms of Froude’s number.

fluid-mechanics-questions-answers-gradually-varied-flow-gvf-1-q7

Answer: a

Explanation: fluid-mechanics-questions-answers-gradually-varied-flow-gvf-1-q7a

8. Estimate the rate of change of specific energy having bed slope S 0 and slope of total energy line S f .

fluid-mechanics-questions-answers-gradually-varied-flow-gvf-1-q8

Answer: c

Explanation:

fluid-mechanics-questions-answers-gradually-varied-flow-gvf-1-q8a

9. Calculate the rate of change of specific energy if the bed slope is 1 in 1000 and S f = 0.00007.

a) 6.3×10 -3 m

b) 7.3×10 -3m

c) 8.3×10 -3 m

d) 9.3×10 -3 m

Answer: d

Explanation: fluid-mechanics-questions-answers-gradually-varied-flow-gvf-1-q9

10. Estimate the value of S f if the value of bed slope is 1 in 800 and and dE ⁄ dx = 10 -3 m.

a) 0.00015

b) 0.00025

c) 0.00035

d) 0.00045

Answer: b

Explanation: dE ⁄ dx = S 0 – S f ; S f = 0.00025.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Gradually Varied Flow – 2”.

1. If the value of rate of change of specific energy is 7.79×10 -4 m and S f = 0.00013, calculate the value of bed slope.

a) 1 in 1000

b) 1 in 1100

c) 1 in 1200

d) 1 in 1300

Answer: b

Explanation: dE ⁄ dx = S 0 – S f ; S 0 = 1 in 1100.

2. Calculate the rate of change of depth of a rectangular channel having depth 1m and width 4m. Given: C = 40, S 0 = 1/900, S f = 0.0005

a) 4.94×10 -4 m

b) 5.94×10 -4 m

c) 6.94×10 -4 m

d) 7.94×10 -4 m

Answer: c

Explanation:

fluid-mechanics-questions-answers-gradually-varied-flow-gvf-2-q2

3. Calculate the rate of change of depth of a triangular channel if the depth is 4m and the side slope is1H:2V. Given:S 0 = 1 in 1500;S f = 0.00004 and n=0.010.

a) 8.95×10 -4 m

b) 9.95×10 -4 m

c) 10.95×10 -4 m

d) 11.95×10 -4 m

Answer: a

Explanation:

fluid-mechanics-questions-answers-gradually-varied-flow-gvf-2-q3

4. Calculate the value of S f for a trapezoidal channel having depth 2m, width 5m and side slope of 1H:1.5V. Given: dy/dx=1.18×10 -3 ,S 0 = 1 in 1000, C = 50.

a) 0.00001

b) 0.00002

c) 0.00003

d) 0.00004

Answer: a

Explanation:

fluid-mechanics-questions-answers-gradually-varied-flow-gvf-2-q4

5. Determine the rate of change of depth of a rectangular channel having dimensions 2m×3m and the velocity of flow is 2 m/s.

Given:S 0 = 1 in 500 and S f = 0.0007.

a) 0.63m

b) 1.63m

c) 2.63m

d) 3.63m

Answer: b

Explanation:

fluid-mechanics-questions-answers-gradually-varied-flow-gvf-2-q5

6. Calculate the velocity of flow in a triangular channel having depth 7m and the side slope of the channel is 1H:4V if the bed slope of the channel is 1 in 1200 and the slope of the energy line is 0.00010. Given:/dx=7.55m.

a) 1 m/s

b) 2 m/s

c) 3 m/s

d) 4 m/s

Answer: a

Explanation:

fluid-mechanics-questions-answers-gradually-varied-flow-gvf-2-q6

7. Calculate the value of bed slope of a trapezoidal channel having depth 2m and width 2.5m with a side slope of1H:3V. Given: dy/dx=1.43×10 -3 ; S f = 0.00002; V = 1.5 m/s.

a) 1 in 1000

b) 1 in 900

c) 1 in 800

d) 1 in 700

Answer: c

Explanation:

fluid-mechanics-questions-answers-gradually-varied-flow-gvf-2-q7

8. The dimensions of a rectangular channel section is2.5m×1m. Calculate the value of S f if the bed slope of the channel is 1 in 600. Given: dy/dx=1.52×10 -3 m.

a) 0.0002

b) 0.0003

c) 0.0004

d) 0.0005

Answer: d

Explanation:

fluid-mechanics-questions-answers-gradually-varied-flow-gvf-2-q8

9. The dimensions of a rectangular channel section is 2.5m×1m. Calculate the rate of change of specific energy if the rate of change of depth is 1.52×10 -3 m.

a) 1.17×10 -3 m

b) 2.00×10 -3 m

c) 2.03×10 -3 m

d) 2.06×10 -3 m

Answer: a

Explanation:

fluid-mechanics-questions-answers-gradually-varied-flow-gvf-2-q9

10. Calculate the value of rate of change of specific energy for a triangular channel having depth 3.5m and the side slope is 1H:2V. Given:V = 2.5 m/s, dy/dx=8.6×10 -4 .

a) 3.47×10 -4 m

b) 4.47×10 -4 m

c) 5.47×10 -4 m

d) 6.47×10 -4 m

Answer: c

Explanation: fluid-mechanics-questions-answers-gradually-varied-flow-gvf-2-q10

This set of Fluid Mechanics Objective Questions & Answers focuses on “Gradually Varied Flow – 3”.

1. Determine the value of the hydraulic depth of a channel having dy ⁄ dx = 4×10 -4 and dE ⁄ dx = 3.73×10 -4 . Given:V = 1m/s

a) 0.5m

b) 1.5m

c) 2.5m

d) 3.5m

Answer: b

Explanation:

fluid-mechanics-objective-questions-answers-q1

2. A rectangular channel has depth of 1m and width of 2m, calculate the rate of change of depth if the rate of change of specific energy is 2×10 -5 m. Given: F r =0.48.

a) 0.60×10 -5 m

b) 1.60×10 -5 m

c) 2.60×10 -5 m

d) 3.60×10 -5 m

Answer: c

Explanation:

fluid-mechanics-objective-questions-answers-q2

3. The top width of a triangular channel section is 6m and the side slope of the channel is 1H:4V, calculate the rate of change of specific energy if dy ⁄ dx = 2×10 -5 m and V=2 m/s

a) 1.86×10 -5 m

b) 2.86×10 -5 m

c) 3.86×10 -5 m

d) 4.86×10 -5 m

Answer: a

Explanation:

fluid-mechanics-objective-questions-answers-q3

4. If dE ⁄ dx = 2.5×10 -4 m and dy ⁄ dx = 3.5×10 -4 m, calculate the value of F r .

a) 0.23

b) 0.33

c) 0.43

d) 0.53

Answer: d

Explanation:

fluid-mechanics-objective-questions-answers-q4

5. The rate of change of specific energy is given by x 2 /2 and x ranges from 0 to 3, calculate the value of specific energy.

a) 2.5m

b) 3.5m

c) 4.5m

d) 5.5m

Answer: c

Explanation:

fluid-mechanics-objective-questions-answers-q5

6. The rate of change of depth is given by 1/x 2 and the rate of change of specific energy is given by 3x 2 with x ranging from 0 to 0.2, calculate the value of Froude’s number.

a) 0.96

b) 0.97

c) 0.98

d) 0.99

Answer: d

Explanation: fluid-mechanics-objective-questions-answers-q6

7. The hydraulic depth of a channel is 0.94m and the velocity of flow is 2 m/s. Calculate the rate of change of depth if the rate of change of specific energy is 2.5×10 -4 m.

a) 2.33×10 -4 m

b) 3.33×10 -4 m

c) 4.33×10 -4 m

d) 5.33×10 -4 m

Answer: c

Explanation:

fluid-mechanics-objective-questions-answers-q7

8. Calculate the value of Froude’s number for a rectangular channel having depth 1.5m and width 2.5m if the value of C = 30 and S 0 =1 in 1000.

a) 0.1

b) 0.2

c) 0.3

d) 0.4

Answer: b

Explanation: fluid-mechanics-objective-questions-answers-q8

9. The dynamic equation for the slope of water surface in a GVF is not valid for super critical flow.

a) True

b) False

Answer: a

Explanation: fluid-mechanics-objective-questions-answers-q9

10. If the ratio of dE ⁄ dx and dy ⁄ dx is 0.2823, estimate the value of Froude’s number.

a) 0.65

b) 0.75

c) 0.85

d) 0.95

Answer: c

Explanation: Ratio = 1 – F r 2 = 0.2823; F r =0.85.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Gradually Varied Flow – 4”.

1. What is the expression for head loss in case of a GVF?

a) h f = L ⁄ 2 S f

b) h f = LS f

c) h f = 2LS f

d) h f = 3LS f

Answer: b

Explanation: Analytically loss is given by the product of length of the back water curve and slope

Therefore, h f = LS f .

2. What is the expression for the length of the backwater curve?

fluid-mechanics-questions-answers-gradually-varied-flow-gvf-4-q2

Answer: c

Explanation:

fluid-mechanics-questions-answers-gradually-varied-flow-gvf-4-q2a

3. Calculate the head loss if the length of the back water curve is 25000m and S f =0.00006.

a) 1m

b) 1.5m

c) 2.0m

d) 2.5m

Answer: b

Explanation: We know that h f =LS f ; h f = 1.5m.

4. Estimate the slope of energy line in a GVF having length of the back water curve 30000m and head loss of 1m.

a) 1.33×10 -5

b) 2.33×10 -5

c) 3.33×10 -5

d) 4.33×10 -5

Answer: c

Explanation: We know that h f =LS f ; S f = 3.33×10 -5 .

5. Determine the length of the back water curve if E 1 =2.8m and E 2 =5.6m. Given:S 0 =0.00009 S f = 0.00004.

a) 26000m

b) 36000m

c) 46000m

d) 56000m

Answer: d

Explanation: fluid-mechanics-questions-answers-gradually-varied-flow-gvf-4-q5

6. If the difference between specific energies is 2m calculate the rate of change of specific energies if the length of the back water curve is 26314m.

a) 6.6×10 -5 m

b) 7.6×10 -5 m

c) 8.6×10 -5 m

d) 9.6×10 -5 m

Answer: b

Explanation:

fluid-mechanics-questions-answers-gradually-varied-flow-gvf-4-q6

7. Calculate the bed slope of the channel if the slope of the energy line 0.00024 and the length of the back water curve is 104166.67m. Given:E 1 -E 2 =3m.

a) 2.28×10 -5

b) 3.28×10 -5

c) 4.28×10 -5

d) 5.28×10 -5

Answer: d

Explanation:

fluid-mechanics-questions-answers-gradually-varied-flow-gvf-4-q7

8. If the depths in a channel are 2m and 4m and the velocities are 0.5 m/s and 0.3m/s, calculate the difference between specific energies.

a) 2m

b) 3m

c) 4m

d) 5m

Answer: a

Explanation:

fluid-mechanics-questions-answers-gradually-varied-flow-gvf-4-q8

9. Calculate the slope of the energy line if the bed slope of the channel is 4.81×10 -5 if the depths of the channel are 2.7m and 4.7m and velocities are 1 m/s and 0.5m/s respectively.

a) 0.00002

b) 0.00003

c) 0.00004

d) 0.00005

Answer: d

Explanation:

fluid-mechanics-questions-answers-gradually-varied-flow-gvf-4-q9

10. The dimensions of a rectangular channel is 3m×2m and the bed slope of the channel is 1 in 1000, calculate the rate of change of depth if the rate of change of specific energy is 2×10 -5 m. Given: n = 0.010

a) 1.43×10 -5 m

b) 2.43×10 -5 m

c) 3.43×10 -5 m

d) 4.43×10 -5 m

Answer: c

Explanation:

fluid-mechanics-questions-answers-gradually-varied-flow-gvf-4-q10

This set of Fluid Mechanics Question Paper focuses on “Gradually Varied Flow – 5”.

1. Specific energy in GVF changes only under which of the following conditions.

a) Difference between bed slope and slope of energy line

b) Both bed slope and energy slope are equal

c) Presence of bed slope alone

d) Presence of energy slope alone

Answer: a

Explanation: We know that dE ⁄ dx = S 0 – S f

Hence if there’s a difference between bed slope and energy slope specific energy changes.

2. The channel is prismatic in case of a GVF.

a) True

b) False

Answer: a

Explanation: In a GVF a flow is steady and the channel section is uniform throughout, hence it is prismatic.

3. Calculate the value of frictional slope for a rectangular channel having width 5m and depth 3m. Given:V=2 m/s and n = 0.012.

a) 2.01×10 -4

b) 3.01×10 -4

c) 4.01×10 -4

d) 5.01×10 -4

Answer: d

Explanation:

fluid-mechanics-question-papers-q3

Friction slope is same as slope of energy line and the same equations are applicable.

4. Calculate the frictional slope of a triangular channel having depth 2.5m and side slope of 1H:2V if the rate of change of specific energy is 1.6×10 -5 m/s. Given:V=1.57 m/s

a) 5.53×10 -4 m

b) 6.53×10 -4 m

c) 7.53×10 -4 m

d) 8.53×10 -4 m

Answer: c

Explanation:

fluid-mechanics-question-papers-q4

5. What happens to the depth of flow when there is an obstruction in the path?

a) Remains the same

b) Increases

c) Decreases

d) Flow stops

Answer: b

Explanation: When the flow is obstructed the depth of flow increases as the water flows over the object. This change in path is called back water curve.

6. Calculate the value of Froude’s number if the ratio of rate of change of specific energy and rate of change of depth is 0.9.

a) 0.29

b) 0.30

c) 0.31

d) 0.32

Answer: c

Explanation:

fluid-mechanics-question-papers-q6

7. Which of the following assumptions is true in case of GVF?

a) The flow is not steady

b) The streamlines are parallel

c) Pressure distribution is not hydrostatic

d) Channel has varying alignment and shape

Answer: b

Explanation: The flow in a GVF is steady and hence the streamline are parallel to each other.

8. The ratio of bed slope and the slope of energy line is 2, calculate the value of slope of energy line if the length of back water curve is 20000m. Given: E 1 =2m and E 2 =5m.

a) 0.5×10 -4

b) 1.0×10 -4

c) 1.5×10 -4

d) 2.0×10 -4

Answer: c

Explanation:

fluid-mechanics-question-papers-q8

9. The depth and widths of a trapezoidal channel section are 2m and 4m respectively and the side slope of 1H;5V, calculate the rate of change of depth if the rate of change of specific energy is 1.5×10 -5 . Given: S 0 =1 in 1000,C=35.

a) 0.5×10 -5 m

b) 1.0×10 -5 m

c) 1.5×10 -5 m

d) 2.0×10 -5 m

Answer: c

Explanation:

fluid-mechanics-question-papers-q9

10. Calculate the head loss in a channel if the length of the back water curve is 30000m and the slope of the energy line is 4× -4 .

a) 8m

b) 10m

c) 12m

d) 14m

Answer: c

Explanation: Consider h L = S f L;h L = 12m.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Gradually Varied Flow in Wide Rectangular Channels”.

1. What is the hydraulic radius for a wide rectangular channel section?

a) 3y

b) 2y

c) y

d) y/2

Answer: c

Explanation: For a wide rectangular channel B>>y

A = By; P = B+2y = B 

R = A ⁄ P = y.

2. Which of the following equations is true for a wide rectangular channel?

fluid-mechanics-questions-answers-gradually-varied-flow-wide-rectangular-channels-q2

Answer: c

Explanation:

fluid-mechanics-questions-answers-gradually-varied-flow-wide-rectangular-channels-q2a

3. Calculate the rate of change of depth of a wide rectangular channel having uniform flow depth of 2m and the depth during GVF is 1.5m. Given:y c =1m, S 0 =1 in 1500.

a) 1.4×10 -4 m

b) 2.4×10 -4 m

c) 3.4×10 -4 m

d) 4.4×10 -4 m

Answer: d

Explanation:

fluid-mechanics-questions-answers-gradually-varied-flow-wide-rectangular-channels-q3

4. Which of the following equations is true considering Chezy’s equation?

fluid-mechanics-questions-answers-gradually-varied-flow-wide-rectangular-channels-q4

Answer: c

Explanation:

fluid-mechanics-questions-answers-gradually-varied-flow-wide-rectangular-channels-q4a

5. Which of the following equations is true considering Manning’s equation?

fluid-mechanics-questions-answers-gradually-varied-flow-wide-rectangular-channels-q5

Answer: a

Explanation: fluid-mechanics-questions-answers-gradually-varied-flow-wide-rectangular-channels-q5a

6. The slope of the energy line of a wide rectangular channel is 4×10 -5 and the bed slope of the channel is 1 in 1200 using manning’s equation, calculate the depth in GVF if the uniform depth of flow is 1.5m.

a) 0.5m

b) 0.6m

c) 0.7m

d) 0.8m

Answer: b

Explanation: fluid-mechanics-questions-answers-gradually-varied-flow-wide-rectangular-channels-q6

7. The value of slope of energy line of a wide rectangular channel is 3×10 -4 and the bed slope of the channel is 1 in 1500 using chezy’s equation, calculate the uniform flow depth if the depth during GVF is 2m.

a) 1.61m

b) 2.61m

c) 3.61m

d) 4.61m

Answer: b

Explanation: fluid-mechanics-questions-answers-gradually-varied-flow-wide-rectangular-channels-q7

8. If y = 2m and velocity of flow is 2.5m⁄s, calculate the critical depth.

a) 0.36m

b) 1.36m

c) 2.36m

d) 3.36m

Answer: b

Explanation: fluid-mechanics-questions-answers-gradually-varied-flow-wide-rectangular-channels-q8

9. Which of the following expressions is true?

fluid-mechanics-questions-answers-gradually-varied-flow-wide-rectangular-channels-q9

Answer: a

Explanation:

fluid-mechanics-questions-answers-gradually-varied-flow-wide-rectangular-channels-q9a

10. Which of the following expressions is true?

fluid-mechanics-questions-answers-gradually-varied-flow-wide-rectangular-channels-q10

Answer: a

Explanation:

fluid-mechanics-questions-answers-gradually-varied-flow-wide-rectangular-channels-q10a

11. If dy/dx=3×10 -4 m and the ratio of bed slope and slope of energy line is 0.7, calculate the value of slope of energy line if the uniform flow depth is 1.6m, critical depth is 1.2m.

a) 5.25×10 -4

b) 6.25×10 -4

c) 7.2510 -4

d) 8.25×10 -4

Answer: d

Explanation:

fluid-mechanics-questions-answers-gradually-varied-flow-wide-rectangular-channels-q11

12. If the ratio of GVF depth to normal depth and the ratio of critical depth to normal are equal to 0.5, calculate the rate of change of depth if the bed slope of the channel is 1 in 1300.

a) 5.96× -4 m

b) 6.96× -4 m

c) 7.96× -4 m

d) 8.96× -4 m

Answer: c

Explanation:

fluid-mechanics-questions-answers-gradually-varied-flow-wide-rectangular-channels-q12

13. Calculate the critical depth of a wide rectangular channel section if the normal depth and y n are 3.2m and 2.5m respectively. Given: dy/dx=3×10 -4 m and S 0 =1/2000.

a) 0.29m

b) 1.29m

c) 2.29m

d) 3.29m

Answer: b

Explanation:

fluid-mechanics-questions-answers-gradually-varied-flow-wide-rectangular-channels-q13

14. For a wide rectangular channel y>>B.

a) True

b) False

Answer: b

Explanation: For a wide rectangular channel B>>y, hence R=y in this case.

15. If the velocity of flow through a wide rectangular channel is 2m⁄s and the rate of change of depth is 3×10 -5 m, calculate the manning’s constant of the channel if the uniform flow depth is 1m and y n =0.6m. Given: Critical depth = 0.5m.

a) 0.38×10 -3

b) 1.38×10 -3

c) 2.38×10 -3

d) 3.38×10 -3

Answer: c

Explanation:

fluid-mechanics-questions-answers-gradually-varied-flow-wide-rectangular-channels-q15

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Relation between Water Surface Slopes and Channel Bottom Slopes”.

1. A slope based on the culvert bottom is called______

a) Hydraulic slope

b) Hydraulic curve

c) Adverse slope

d) Horizontal slope

Answer: a

Explanation: Hydraulic slope is defined as a slope of a culvert at a specific flow. It is classified into the hydraulic regime. It defines the type of solution generated from the gradual variation in the flow calculations.

2. A slope based on a relationship between water depth and critical depth is called_______

a) Hydraulic slope

b) Hydraulic curve

c) Adverse slope

d) Horizontal slope

Answer: b

Explanation: Hydraulic curve is defined as curve that is based on the relationship of the water depth relative to the critical depth and its normal depth. Thus, the correct choice is hydraulic curve.

3. The compressible flow is assumed to be _____________

a) Isentropic

b) Adiabatic

c) Polytropic

d) Isentropic and adiabatic

Answer: a

Explanation: Compressible flow is a branch of fluid mechanics that deals with different types of flow. Its main significance lies in the change in fluid density. It deals with gas dynamics. Flow is assumed to be isentropic.

4. What is the culvert bottom slope denoted as?

a) sl

b) SL

c) So

d) sL

Answer: c

Explanation: Culvert bottom slope is denoted as ‘So’. The culvert bottom slope plays an important role in determining the hydraulic slope and hydraulic curve of a fluid flow in motion. It is found using appropriate inlet and outlet conditions.

5. What is the critical depth denoted as?

a) Yo

b) Y c

c) Yb

d) d

Answer: b

Explanation: Critical depth is denoted as Y c . The critical depth plays an important role in determining the hydraulic slope and hydraulic curve of a fluid flow in motion. It is found using appropriate inlet and outlet conditions.

6. What is the normal depth denoted as?

a) Yo

b) Y c

c) Yb

d) Y n

Answer: d

Explanation: Normal depth is denoted as Y n . The normal depth plays an important role in determining the hydraulic slope and hydraulic curve of a fluid flow in motion. It is found using appropriate inlet and outlet conditions.

7. When So is less than zero, it is called________

a) Adverse

b) Horizontal

c) Critical

d) Mild

Answer: a

Explanation: When S o is less than zero, it is called Adverse slopes. The flow conditions for an adverse slope is similar to that of the horizontal case in that non-existence state. Adverse slope is always negative.

8. When S o is equal to zero, it is called________

a) Adverse

b) Horizontal

c) Critical

d) Mild

Answer: b

Explanation: When S o is equal to zero, it is called Horizontal slope. It is denoted as H. The bed slope follows the manning’s equation to solve for its normal depth. It is always equal to zero.

9. When Y o = Y c , it is called ________

a) Adverse

b) Horizontal

c) Critical

d) Mild

Answer: c

Explanation: When Yo= Yc, it is called a Critical slope. Critical slopes are denoted by the letter ‘c’. Critical slopes like the other slopes have three depth zones that help to determine the water surface flow.

10) When Y n > Y c and S o > 0, it is called a _____

a) Adverse

b) Horizontal

c) Critical

d) Mild

Answer: d

Explanation: When Y n > Y c and S o > 0, it is called a mild slope. Mild slope is denoted by ‘M’. This is a bed slope that has 3 zones with a different set of conditions. This slope occurs most commonly in the back water curve.

11. When S o > 0 and Y n < Y c , it is called as_______

a) Adverse

b) Horizontal

c) Critical

d) Steep

Answer: d

Explanation: When the slopes have a condition of S o > 0 and Y n < Y c , it is called as steep slope. It is denoted as ‘S’. Steep slope is classified into three zones. These zone are differentiated depending on their conditions and properties.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Characteristics of Surface Profiles”.

1. A surface profile is a measure of _______

a) Temperature changes

b) Pressure changes

c) Flow changes

d) Volumetric changes

Answer: c

Explanation: Surface profile is a measure of flow changes that are developed in the fluid body. It is developed longitudinally. Thus, the reason for the surface profile is due to flow changes in the system.

2. The surface profile is classified into normal depth and critical depth.

a) True

b) False

Answer: a

Explanation: Surface profile is a measure of flow changes that are developed in the fluid body. It is developed longitudinally. It is divided into normal depth and critical depth. Thus, the answer is true.

3. What is the condition for a normal depth?

a) Water depth remains a constant

b) Temperature of fluid remains a constant

c) Pressure of fluid remains a constant

d) Isentropic and adiabatic flow

Answer: a

Explanation: Normal depth is a depth of flow in the channel. It is created when the slope of the water surface and channel bottom is the same and the water depth remains the same throughout the entire flow.

4. When gravitational force is equal to the friction drag, what type of depth is formed?

a) Critical depth

b) Normal depth

c) Cylindrical depth

d) Conical depth

Answer: b

Explanation: Normal depth is a depth of flow in the channel. It is created when the slope of the water surface and channel bottom is the same and the water depth remains the same throughout the entire flow. It is formed when gravitational force is equal to the friction drag.

5. When the depth is normal, which parameter is zero?

a) Pressure

b) Temperature

c) Volume

d) Acceleration

Answer: d

Explanation: Normal depth is a depth of flow in the channel. It is created when the slope of the water surface and channel bottom is the same and the water depth remains the same throughout the entire flow. During a normal formation of a normal depth, there is no acceleration of flow.

6. Which among the following is the Manning’s equation?

a) Q = A/v

b) Q = vA

c) Q = v+A

d) Q = v-A

Answer: b

Explanation: Manning’s equation is one of the most commonly used equations governing the open channel glow. It is an alternative to the Chezy’s equation. It is an empirical equation that applies to uniform flow in open channels.

7. Manning’s equation is not used to calculate_________

a) Normal depth

b) Roughness

c) Critical depth

d) Hydraulic radius

Answer: c

Explanation: Manning’s equation is an empirical equation that applies to uniform flow in open channels. Manning’s equation is used to calculate normal depth, roughness, wetted area and the hydraulic radius.

8. When the energy is at minimum for flow discharge, it is called _________

a) Normal depth

b) Roughness

c) Critical depth

d) Hydraulic radius

Answer: c

Explanation: Critical depth is defined as the depth at which the energy is at minimum for flow discharge. The flow of profile is classified into three zones for a better understanding. Thus, The correct answer is Critical depth.

9. Normal depth occurs only for a uniform and steady flow.

a) True

b) False

Answer: a

Explanation: Normal depth occurs only for a uniform and steady flow. Normal depth is a depth of flow in the channel. It is created when the slope of the water surface and channel bottom is the same and the water depth remains the same throughout the entire flow.

10. Subcritical depth occurs when_________

a) Actual water depth > Critical depth

b) Actual water depth < Critical depth

c) Actual water depth = Critical depth

d) They are independent

Answer: a

Explanation: Subcritical depth occurs when actual water depth is greater than the critical depth. It is dominated by gravitational forces and behaves in a slow and stable way.

11. During a subcritical flow, what is value of Froude’s number?

a) Zero

b) Greater than one

c) Less than one

d) Not defined

Answer: c

Explanation: Subcritical depth occurs when actual water depth is greater than the critical depth. It is dominated by gravitational forces and behaves in a slow and stable way. The Froude’s number is less than one during a subcritical flow.

12. Supercritical depth occurs when_________

a) Inertial forces behave as unstable flow

b) Roughness is high

c) Critical depth increases

d) Hydraulic radius expands

Answer: a

Explanation: Supercritical depth occurs when the inertial forces behaves as a rapid and an unstable flow. Supercritical flow transition to subcritical flow takes place through a hydraulic jump due to high energy loss.

13. During a supercritical flow, what is value of Froude’s number?

a) Zero

b) Greater than one

c) Less than one

d) Not defined

Answer: b

Explanation: Supercritical depth occurs when the inertial forces behaves as a rapid and an unstable flow. Supercritical flow transition to subcritical flow takes place through a hydraulic jump due to high energy loss. It has a Froude number greater than one.

14. During a critical flow, what is value of Froude’s number

a) Zero

b) Greater than one

c) Less than one

d) Equal to one

Answer: d

Explanation: Critical flow is a flow in which the control flow possesses the minimum possible energy for a particular flow rate. Critical flow has a Froude’s number equal to one.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Hydraulic Jump”.

1. Hydraulic jump is observed in _______

a) Closed channel flow

b) Open channel flow

c) Flow changes

d) Volumetric changes

Answer: b

Explanation: Hydraulic pump is a phenomenon in science that deals with hydraulics. It is observed in an open channel flow. Some of the examples of open channel flows are rivers and spillways.

2. Hydraulic jump depends upon

a) Temperature

b) Pressure

c) Initial fluid speed

d) Volumetric changes

Answer: c

Explanation: Hydraulic pump is a phenomenon in science that deals with hydraulics. It is observed in an open channel flow. It depends on the initial speed of the fluid. Thus, option Initial fluid speed is the correct answer.

3. In which case is the hydraulic jump not possible?

a) Initial speed > critical speed

b) Initial speed < critical speed

c) Initial speed = critical speed

d) Independent

Answer: b

Explanation: Hydraulic jump is not possible when the initial speed is less than the critical speed. There is a transition that is created during the change. The transition appears as an undulating wave. With the increase in the initial flow, the transition becomes abrupt.

4. Open channel flow takes place _______

a) On a free surface

b) In the pipe

c) Within a cylindrical depth

d) In a pump

Answer: a

Explanation: Open channel flow is a flow that deals with hydraulics in fluid mechanics. It is a type of liquid flow that flows through a free surface. This free surface is called as a channel. And since the channel is free, it is called as an open channel flow.

5. When the hydraulic jump is in a moving form it is called _________

a) Negative surge

b) Positive surge

c) Turbulent surge

d) Accelerated surge

Answer: b

Explanation: When the hydraulic jump is dynamic or in a moving form it is called as positive surge. Hydraulic jump can be stationery or dynamic. Hydraulic jump can be described using the same analytical approaches.

6. Fluid speed before the hydraulic jump is ________

a) Critical

b) Supercritical

c) Subcritical

d) Dynamic

Answer: b

Explanation: Fluid speed before the hydraulic jump is supercritical. It is said to be supercritical because it is faster than the wave speed. It is also called as shooting speed or superundal.

7. Fluid height before the hydraulic jump is ________

a) Normal

b) Low

c) High

d) Zero

Answer: b

Explanation: Hydraulic jump is not possible when the initial speed is less than the critical speed. There is a transition that is created during the change. The transition appears as an undulating wave. Fluid height before the hydraulic jump is low.

8. Fluid height after the hydraulic jump is ________

a) Normal

b) Low

c) High

d) Zero

Answer: c

Explanation: Hydraulic jump is not possible when the initial speed is less than the critical speed. There is a transition that is created during the change. The transition appears as an undulating wave. Fluid height after the hydraulic jump is high.

9. Fluid flow before the hydraulic jump is ______

a) Normal

b) Rough

c) Smooth

d) Zero

Answer: c

Explanation: Hydraulic jump is not possible when the initial speed is less than the critical speed. There is a transition that is created during the change. Fluid flow before the hydraulic jump is typically smooth turbulent flow.

10. Fluid flow after the hydraulic jump is ______

a) Normal

b) Rough

c) Smooth

d) Zero

Answer: b

Explanation: Hydraulic jump is not possible when the initial speed is less than the critical speed. There is a transition that is created during the change. Fluid flow after the hydraulic jump is typically rough and choppy turbulent flow.

11. During a subcritical flow, what is the value of Froude’s number?

a) Zero

b) Greater than one

c) Less than one

d) Not defined

Answer: c

Explanation: Subcritical depth occurs when actual water depth is greater than the critical depth. It is dominated by gravitational forces and behaves in a slow and stable way. The Froude’s number is less than one during a subcritical flow.

12. Which hydraulic jump occurs in our sink?

a) Inertial forces hydraulic jump

b) Shallow fluid hydraulic jump

c) Critical depth jump

d) Hydraulic radius expands

Answer: b

Explanation: Shallow fluid hydraulic jump takes place during a hydraulic jump that is created in our sink. It will undergo a smooth flow during the hydraulic jump as the flow is shallow.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Types of Hydraulic Jumps”.

1. When a shallow water flowing radially slows down due to______

a) Friction

b) Temperature

c) Pressure

d) Volume

Answer: a

Explanation: The water that flowing radially slows down due to friction in the fluid. This happens as the fluid grows shallower, which keeps it dilatory. Due to this, the Froude number drops to the point where the jump occurs.

2. Changes in the behaviour of the jump can be observed by changing the _______

a) Temperature

b) Pressure

c) Flow rate

d) Volumetric changes

Answer: c

Explanation: Hydraulic pump is a phenomenon in science that deals with hydraulics. It is observed in in an open channel flow. It depends on the initial speed and flow rate of the fluid. Thus, option Pressure is the correct answer.

3. Which hydraulic jump is used in abysmal fan formation?

a) Shallow fluid

b) Internal wave

c) External wave

d) Atmospheric

Answer: b

Explanation: Hydraulic jump is not possible when the initial speed is less than the critical speed. There is a transition that is created during the change. The transition appears as an undulating wave. Turbidity currents result in internal hydraulic jumps.

4. Which among the following is a parameter that does not account for a change of Internal hydraulic jump?

a) Temperature

b) Salinity

c) Density

d) Depth

Answer: d

Explanation: Depth is a parameter that does not play a role in the hydraulic jump. The internal hydraulic jump have association with temperature induced stratification, salinity and density differences due to suspended materials.

5. When the hydraulic jump is in a moving form it is called _________

a) Negative surge

b) Positive surge

c) Turbulent surge

d) Accelerated surge

Answer: b

Explanation: When the hydraulic jump is dynamic or in a moving form it is called as positive surge. Hydraulic jump can be stationery or dynamic. Hydraulic jump can be described using the same analytical approaches.

6. Where is hydraulic jump used in industrial applications?

a) Spillways

b) Pipes

c) Pumps

d) Filters

Answer: a

Explanation: The hydraulic jump is one of the most used design choices by engineers in industrial applications. It is used to dissipate energy in spillways and outlets. A well-defined outlet can produce 60 to 70 percent energy.

7. When a shallow water flowing radially slows down due to ______

a) Friction

b) Temperature

c) Pressure

d) Volume

Answer: a

Explanation: The water that flowing radially slows down due to friction in the fluid. This happens as the fluid grows shallower, which keeps it dilatory. Due to this, the Froude number drops to the point where the jump occurs.

8. With the increase in speed of the surface tension, the waves bleed of ________

a) Zero frequency

b) High frequency

c) Low frequency

d) Equal to one

Answer: b

Explanation: With the increase in speed of the surface tension, the waves bleed of High frequency. It makes an undular jump into a dominant form. The flow depth is just enough that the surface tension can be no longer neglected.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Location of a Hydraulic Jump”.

1. Hydraulic jump in a rectangular channel is also called _________

a) Closed channel jump

b) Open channel jump

c) Rectangular jump

d) Shallow fluid jump

Answer: c

Explanation: Hydraulic pump is a phenomenon in science that deals with hydraulics. It is observed in an open channel flow. When it occurs in a rectangular channel. It is known as classical jump. It is a natural phenomenon.

2. Classical jump occurs when________

a) Temperature changes

b) Pressure changes

c) Supercritical to subcritical change

d) Volumetric changes

Answer: c

Explanation: Classical jump is a phenomenon in science that deals with hydraulics. It is observed in an open channel flow. It depends on the initial speed of the fluid. Classical jump occurs due to the change from supercritical to subcritical condition.

3. Which among the following is not the purpose of a hydraulic jump?

a) Mix chemicals

b) Dissipate heat

c) Increasing temperature and pressure

d) Aeration device

Answer: c

Explanation: Hydraulic jump is not possible when the initial speed is less than the critical speed. There is a transition that is created during the change. This transition leads to mixing of chemicals, dissipating heat and used in aeration devices.

4. How do we produce equations describing the jump?

a) Conserving the momentum

b) Conserving the mass

c) Conserving the pressure

d) Conserving the heat

Answer: a

Explanation: In a hydraulic jump, the equations are produced by conservation of the momentum. It is mainly used to apply in equations that have unknown energy losses. Thus, we must develop the equation for a better understanding.

5. An example of common hydraulic jump is________

a) Surge tank

b) Pump

c) Sink

d) Air cooler

Answer: c

Explanation: An example of a common hydraulic jump is a sink. It is used in our day to day life. This sort of jump can be used to form a circular, stationary wave and the inflow of water. Thus, the correct option is Sink.

6. Fluid speed before the hydraulic jump is ________

a) Coagulation chamber

b) Pump

c) Sink

d) Air cooler

Answer: a

Explanation: Fluid speed before the hydraulic jump is a coagulation chamber. The hydraulic jumps made by man have primary focuses. The primary focus that scientists have been focussing on is viscosity.

7. Give an example of man-made hydraulic jumps?

a) Normal

b) Low

c) High

d) Zero

Answer: b

Explanation: Hydraulic jump is not possible when the initial speed is less than the critical speed. There is a transition that is created during the change. The transition appears as an undulating wave. Fluid height before the hydraulic jump is low.

8. Energy is not conserved throughout the hydraulic jump.

a) True

b) False

Answer: a

Explanation: Hydraulic jump is not possible when the initial speed is less than the critical speed. There is a transition that is created during the change. Though momentum is conserved throughout the hydraulic jump, energy is not conserved.

9. Length of a hydraulic pump is often difficult to measure due to _________

a) Changes in turbulence

b) Temperature changes

c) Pressure changes

d) Volumetric changes

Answer: a

Explanation: Length of a hydraulic pump is often difficult to measure due to investigations that occur due to sudden changes in turbulence. The length of the hydraulic pump plays an important role in setting up the basins.

10. Height of the hydraulic is similar to its length and is used to know the design of water structures.

a) True

b) False

Answer: a

Explanation: Hydraulic jump is not possible when the initial speed is less than the critical speed. There is a transition that is created during the change. Height of the hydraulic is similar to its length and is used to know the design of water structures.

11. During a subcritical flow, what is value of Froude’s number?

a) Zero

b) Greater than one

c) Less than one

d) Not defined

Answer: c

Explanation: Sub critical depth occurs when actual water depth is greater than the critical depth. It is dominated by gravitational forces and behaves in a slow and stable way. The Froude’s number is less than one during a subcritical flow.

12. During a weak jump, the value of Froude lies in between________

a) 1 to 2.5

b) 2.5 to 3.5

c) Less than 1

d) Zero

Answer: a

Explanation: Weak jump is a jump that takes place, when the Froude’s number lies in between 1 to 2.5. The surfaces that result due to weak jump have a very little energy dissipated.

13. During an oscillating jump, the value of Froude lies in between________

a) 1 to 2.5

b) 2.5 to 4.5

c) Less than 1

d) Zero

Answer: a

Explanation: An oscillating jump is a jump that takes place when the Froude’s number is in between 2.5 to 4.5. During this jump, the jet water at the entrance of the jump fluctuates. It fluctuates from the bottom of the channel to the top of the channel.

14. During a steady jump, the value of Froude lies in between________

a) 1 to 2.5

b) 2.5 to 4.5

c) Less than 1

d) 4.5 to 9

Answer: d

Explanation: A steady jump is a jump that takes place when the Froude’s number is in between 4.5 to 9. In this jump the turbulence is confined within the jump and the location of the jump is susceptible to downstream flow.

15. During a strong jump, the value of Froude lies in between________

a) 1 to 2.5

b) Greater than 9

c) Less than 1

d) 4.5 to 9

Answer: b

Explanation: A strong jump is a jump that takes place when the Froude’s number is greater 9. In this jump, there is a large difference in the conjugate depths. They are characterised by different jump actions that result in a high energy dissipation.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Specific Force”.

1. Which among the following provides the third principle in fluid mechanics?

a) Conservation of mass

b) Conservation of linear momentum

c) Conservation of Heat

d) Conservation of volume

Answer: b

Explanation: In fluid mechanics, the third principle is given by the conservation of linear momentum. It is in addition to the continuity of mass and conservation of energy. They are mostly seen in channel flow problems.

2. Momentum principle states that all the forces acting in the system result in a change in momentum.

a) True

b) False

Answer: a

Explanation: Momentum principle states that all the forces acting in the system result a change in momentum. It is in addition to the continuity of mass and conservation of energy. Thus, the correct option is “true”.

3. Which among the following is not a force that acts in the downstream of the fluid flow?

a) Pressure

b) Weight

c) Friction

d) Gravity

Answer: c

Explanation: Frictional force is a force that does not act in the downstream of the fluid flow. Friction acts in the upstream direction, as friction always opposes the flow of fluid through a stream developing a viscous flow.

4. Which among the following is present in pipe flow?

a) Viscous force

b) Inertial force

c) Gravity force

d) Pressure force

Answer: d

Explanation: Pressure is a force that is applied perpendicular to the surface of an object over a unit area of force. It is defined as the product of pressure intensity and cross-sectional area of the flowing fluid. Pressure force is present in the case of pipe flow.

5. What is momentum?

a) Mass * acceleration

b) Mass * Volume

c) Mass flow rate * velocity

d) Mass flow rate* density

Answer: c

Explanation: Momentum is an expression that is made up of two main functions. These two terms play a significance role in determining the function. The two terms are mass flow rate and velocity. Thus, the final formula is mass flow rate * velocity.

6. A force that is needed to bring back the body to its original position is called as?

a) Viscous force

b) Elastic force

c) Gravity force

d) Pressure force

Answer: c

Explanation: Elastic force is the force that brings a body back to its original position. It is defined as the product of elastic stress and the area of the flowing fluid.

7. What is a specific force denoted as?

a) N

b) F

c) M

d) S

Answer: c

Explanation: Specific force is defined as the force that is expressed in terms of its momentum. It is the momentum of flow passing through a channel of cross section per unit time per unit weight and a second is a force per unit weight. This sum is called the specific force.

8. Energy is not conserved throughout the pipe.

a) True

b) False

Answer: a

Explanation: It is not possible when the initial speed is less than the critical speed. There is a transition that is created during the change. Though momentum is conserved throughout the hydraulic jump, energy is not conserved.

9. Specific force is __________ to mass flow rate.

a) Directly proportional

b) Inversely proportional

c) Independent

d) Not proportional

Answer: a

Explanation: Specific force is directly proportional to the mass flow rate. Specific force is defined as the force that is expressed in terms of it momentum. It is the momentum of flow passing through a channel of cross section per unit time per unit weight and a second is the force per unit weight.

10. Specific force is __________ to cross sectional area.

a) Directly proportional

b) Inversely proportional

c) Independent

d) Not proportional

Answer: a

Explanation: Specific force is inversely proportional to the mass flow rate. Specific force is defined as the force that is expressed in terms of it momentum. It is the momentum of flow passing through a channel of cross section per unit time per unit weight and a second is the force per unit weight.

This set of Fluid Mechanics written test Questions & Answers focuses on “Force Exerted by a Jet on a Stationary Flat Inclined Plate”.

1. Force exerted by a jet on a stationery plate happens in how many cases?

a) 3 cases

b) 2 cases

c) 1 case

d) Nil

Answer: a

Explanation: Force exerted by a jet on a stationery plate happens in three cases. The three cases are classified depending on their position. The three cases are when plate is vertical, plate is inclined and plate is curved with respect to the jet.

2. Force exerted by a jet on a moving plate happens in how many cases?

a) 3 cases

b) 2 cases

c) 1 case

d) Nil

Answer: a

Explanation: Force exerted by a jet on a moving plate happens in three cases. The three cases are classified depending on their position. The three cases are when the plate is vertical, plate is inclined and plate is curved with respect to the jet.

3. In a stationery vertical plate, the jet after striking the plate will move _______

a) In opposite direction

b) Along the plate

c) Perpendicular to the plate

d) Parallel to the plate

Answer: b

Explanation: In a stationery vertical plate, the jet after striking the plate will move along the plate. It moves with respect to the angles that are developed with the plate.

4. At what angle does the jet deflect after striking a stationery vertical plate?

a) 30

b) 60

c) 90

d) 0

Answer: c

Explanation: In a stationery vertical plate, the jet after striking the plate will move along the plate. It moves with respect to the angles that are developed with the plate. Hence, after striking the plate it will get deflected at an angle of 90 degrees.

5. The velocity component after striking the surface will be________

a) One

b) Zero

c) Infinity

d) Negative

Answer: b

Explanation: In a stationery vertical plate, the jet after striking the plate will move along the plate. It moves with respect to the angles that are developed with the plate. The velocity component after striking the surface will be zero.

6. Which among the following is the formula for Force when it strikes the plate?

a) pav 2

b) pav

c) pa

d) maE

Answer: a

Explanation: The rate of change of momentum in the direction of the force is given by the formula pav 2 . Where p = Density of the fluid flow, a = acceleration of the fluid particle and v= velocity of the fluid flowing.

7. To derive pav 2 , we take final velocity minus the initial velocity.

a) True

b) False

Answer: b

Explanation: The rate of change of momentum in the direction of the force is given by the formula pav 2 . Where p = Density of the fluid flow, a = acceleration of the fluid particle and v= velocity of the fluid flowing. To derive pav 2 , we take initial velocity minus the final velocity.

8. The mass of water per sec striking the plate is_________

a) pav 2

b) pav

c) pa

d) maE

Answer: b

Explanation: The mass of water per sec striking the plate is given by pav. Where p = Density of the fluid flow, a = acceleration of the fluid particle and v = velocity of the fluid flowing. Thus, the correct option is pav.

9. Which among the following is formula for force when it acts along the direction of flow?

a) pav 2 Sin 2 θ

b) pav Sin 2 θ

c) pa Sin 2 θ

d) maE Sin 2 θ

Answer: a

Explanation: When a force can be resolved into two components, one in the direction of the jet and the other perpendicular to the jet. The formula for force when it acts along the direction of flow is equal to pav 2 Sin 2 θ.

10. Which among the following is a formula for force when it acts perpendicular to the direction of flow?

a) pav 2 SinθCosθ

b) pav Sin 2 θ

c) pa Sin 2 θ

d) maE Sin 2 θ

Answer: a

Explanation: When a force can be resolved into two components, one in the direction of the jet and the other perpendicular to the jet. The formula for force when it acts perpendicular to the direction of flow is equal to pav 2 SinθCosθ.

11. A jet strikes a curved plate at its ______

a) Sides

b) Surface

c) Centre

d) Does not strike

Answer: c

Explanation: A jet strikes a curved plate at its center. Force exerted by a jet on a stationery plate happens in three cases. The three cases are classified depending on their position. The three cases are when plate is vertical, plate is inclined and plate is curved with respect to the jet.

12. During a weak jump, the value of Froude lies in between________

a) 1 to 2.5

b) 2.5 to 3.5

c) Less than 1

d) Zero

Answer: a

Explanation: Weak jump is a jump that takes place, when the Froude’s number lies in between 1 to 2.5. The surfaces that result due to weak jump have a very little energy dissipated. Thus, option 1 to 2.5 is the correct one.

13. During an oscillating jump, the value of Froude lies in between________

a) 1 to 2.5

b) 2.5 to 4.5

c) Less than 1

d) Zero

Answer: a

Explanation: An oscillating jump is a jump that takes place when the Froude’s number is in between 2.5 to 4.5. During this jump, the jet water at the entrance of the jump fluctuates. It fluctuates from the bottom of the channel to the top of the channel.

14. A jet after striking a smooth plate comes out with a __________ velocity.

a) Increased

b) Decreased

c) Same

d) Zero

Answer: c

Explanation: Force exerted by a jet on a stationery plate happens in three cases. The three cases are classified depending on their position. After it strikes a smooth plate, its velocity remains the same.

15. Component of velocity in direction of jet is -VCosθ

a) True

b) False

Answer: a

Explanation: Component of velocity in direction of jet is -VCosθ. The negative sign indicates the that the taken velocity at the outlet is opposite to the jet of water coming out from the nozzle. Thus, it is true.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Force Exerted by a Jet on a Stationary Curved Plate”.

1. Jet propulsion is a method of generating propulsive force by reaction of ________

a) Accelerating mass

b) Volume

c) Mass flow rate

d) Velocity

Answer: a

Explanation: Force exerted by a jet on a stationery plate happens in three cases. The three cases are classified depending on their position. Jet propulsion is a method of generating propulsive force by reaction of accelerating mass.

2. The propulsive force drives the jet in the ________

a) Backward direction

b) Forward direction

c) Perpendicular direction

d) Parallel movement

Answer: b

Explanation: Force exerted by a jet on a moving plate happens in three cases. The three cases are classified depending on their position. The propulsive force drives the jet in the forward direction. A good example is the aircraft or a boat.

3. In a stationery vertical plate, the jet after striking the plate will move _______

a) In opposite direction

b) Along the plate

c) Perpendicular to the plate

d) Parallel to the plate

Answer: b

Explanation: In a stationery vertical plate, the jet after striking the plate will move along the plate. It moves with respect to the angles that are developed with the plate.

4. Jet propulsion works on the principle of________

a) Newton’s first law

b) Newton’s second law

c) Newton’s third law

d) Thermodynamic properties

Answer: c

Explanation: Jet propulsion works on the principle of Newton’s third law. Newton’s third law states that for every action, there is an equal and opposite reaction. Thus, the correct option is Newton’s third law.

5. What does C v in jet propulsion equation stand for?

a) Area of orifice

b) Velocity

c) Temperature coefficient

d) Velocity coefficient

Answer: d

Explanation: In a jet propulsion, C v stands for velocity coefficient. The main application in which this equation is applied is for a jet propulsion in the tank with orifice. Thus, the correct option is coefficient of velocity in the orifice.

6. Which among the following is the formula for Force when it strikes the plate?

a) pav 2

b) pav

c) pa

d) maE

Answer: a

Explanation: The rate of change of momentum in the direction of force is given by the formula pav 2 . Where p= Density of the fluid flow, a = acceleration of the fluid particle and v = velocity of the fluid flowing.

7. The movement of ships and boats in water is due to __________

a) Water currents

b) Jet propulsion

c) Mass flow rate

d) Volumetric changes

Answer: b

Explanation: The movement of ships and boats in water is due to Jet propulsion. This mainly happens at the back of the ship or boat. It occurs as it exerts force on the ship and the boat. Thus, the correct option is Jet propulsion.

8. The inlet orifices are at what angle with the motion of the ship?

a) 0

b) 30

c) 60

d) 90

Answer: d

Explanation: The inlet orifices are at right angles with respect to the motion of the ship. The main purpose of the inlet orifice is to take water from the sea by the pump. Thus, the correct angle at which it moves is 90 degress.

9. Through inlet orifices, which are facing the direction of motion of the ship, the water from the sea can be taken by the pump.

a) True

b) False

Answer: a

Explanation: Through inlet orifices, which are facing the direction of motion of the ship, the water from the sea can be taken by the pump. We can also take the sea water from the pump when the inlet orifices are at right angles with respect to the motion of the ship.

10. Which among the following is a formula for force when it acts perpendicular to the direction of flow?

a) pav 2 SinθCosθ

b) pav Sin 2 θ

c) pa Sin 2 θ

d) maE Sin 2 θ

Answer: a

Explanation: When a force can be resolved into two components, one in the direction of the jet and the other perpendicular to the jet. The formula for force when it acts perpendicular to the direction of flow is equal to pav 2 SinθCosθ.

11. A jet strikes a curved plate at its ______

a) Sides

b) Surface

c) Centre

d) Does not strike

Answer: c

Explanation: A jet strikes a curved plate at its centre. Force exerted by a jet on a stationery plate happens in three cases. The three cases are classified depending on their position. The three cases are when plate is vertical, plate is inclined and plate is curved with respect to the jet.

12. Which among the following is the formula for relative velocity?

a) V + u

b) Vu

c) V – u

d) V/u

Answer: a

Explanation: Absolute relative velocity of a fluid related to the jet propulsion of the ship when the inlet orifices are at right angles to the direction of the motion of the ship is given by V+u.

13. What is the equation for efficiency of jet propulsion?

a) 2u/

b) 2u/

c) 2u/v

d) V/2u

Answer: b

Explanation: The efficiency of a jet propulsion of the ship when the inlet orifices are at right angles to the direction of the motion of the ship is given by 2u/.

14. A jet after striking a smooth plate comes out with a __________ velocity.

a) Increased

b) Decreased

c) Same

d) Zero

Answer: c

Explanation: Force exerted by a jet on a stationery plate happens in three cases. The three cases are classified depending on their position. After it strikes a smooth plate, its velocity remains the same.

15. Component of velocity in direction of jet is -VCosθ. What does ‘θ’ indicate?

a) Angle made by jet

b) Angle made by jet and outlet tip

c) Angle made by jet and inlet tip

d) Tangent angle

Answer: c

Explanation: Component of velocity in direction of jet is -VCosθ. The negative sign indicates the that the taken velocity at the outlet is opposite to the jet of water coming out from the nozzle. ‘θ’ indicates the angle made by jet and inlet tip of the curved plate.

This set of Fluid Mechanics Multiple Choice Questions & Answers  focuses on “Force Exerted by a Jet on a Series of Vanes”.

1. Principle of fluid mechanics works on the utilization of________

a) Accelerating mass

b) Volume

c) Work

d) Velocity

Answer: c

Explanation: The Principle of fluid mechanics works on the utilization of useful work. The working is based on the force exerted by a fluid jet striking the surface and moving over a series of vanes about its axis.

2. The propulsive force drives the jet in the ________

a) Backward direction

b) Forward direction

c) Perpendicular direction

d) Parallel movement

Answer: b

Explanation: Force exerted by a jet on a moving plate happens in three cases. The three cases are classified depending on their position. The propulsive force drives the jet in the forward direction. A good example is the aircraft or a boat.

3. The force analysis on a curved vane is understood using______

a) Velocity triangles

b) Angle of the plate

c) Vane angles

d) Plate dimensions

Answer: a

Explanation: The force analysis on a curved vane is understood using clearly using the study of velocity triangles. There are two types of velocity triangles, inlet velocity triangle and outlet velocity triangle.

4. Jet propulsion works on the principle of________

a) Newton’s first law

b) Newton’s second law

c) Newton’s third law

d) Thermodynamic properties

Answer: c

Explanation: Jet propulsion works on the principle of Newton’s third law. Newton’s third law states that for every action, there is an equal and opposite reaction. Thus, the correct option is Newton’s third law.

5. How is absolute velocity at inlet denoted?

a) V

b) V 1

c) C

d) v

Answer: b

Explanation: In a jet propulsion, V 1 stands for absolute velocity at the inlet. The main application in which this equation is applied is for a jet propulsion in the tank with orifice. Thus, the correct option is ‘b’.

6. The relative velocity is obtained by the equation_________

a) u – V 1

b) V1

c) u*V 1

d) u/V 1

Answer: a

Explanation: The relative velocity of the jet is denoted as V r1 . It is the relative velocity at the inlet to the vane. Relative velocity of inlet to the vane is obtained by subtracting vectorially the velocity of the vane with its absolute velocity.

7. If the friction is neglected, then_______

a) V r1 > V r2

b) V r1 < V r2

c) V r1 = V r2

d) V r1 is a zero

Answer: c

Explanation: The relative velocity of the jet is denoted as V r1 . It is the relative velocity at the inlet to the vane. Relative velocity of inlet to the vane is obtained by subtracting vectorially the velocity of the vane with its absolute velocity. It happens in the same way for V r2 . Thus, If the friction is neglected, then V r1 = V r2 .

8. If the pressure remains a constant, then ________

a) V r1 > V r2

b) V r1 < V r2

c) V r1 = V r2

d) V r1 is a zero

Answer: c

Explanation: The relative velocity of the jet is denoted as V r1 . It is the relative velocity at the inlet to the vane. Relative velocity of inlet to the vane is obtained by subtracting vectorially the velocity of the vane with its absolute velocity. It happens in the same way for V r2 . Thus, If the pressure remains a constant, then V r1 = V r2 .

9. Through inlet orifices, which are facing the direction of motion of the ship, the water from the sea can be taken by the pump.

a) True

b) False

Answer: a

Explanation: Through inlet orifices, which are facing the direction of motion of the ship, the water from the sea can be taken by the pump. We can also take the sea water from the pump when the inlet orifices are at right angles with respect to the motion of the ship.

10. The efficiency of the vane is given by_________

a) 1-V 2 2 / V 1 2

b) 1-(V 2 2 / V 1 2 )

c) V 2 2 / V 1 2

d) 1- V 1 2

Answer: a

Explanation: In a velocity triangle at the inlet and the outlet, the control volume is moving with a uniform velocity. Therefore, the momentum theorem of the control volume is at a steady flow. Thus, the efficiency of the vane is given by 1-(V 2 2 / V 1 2 ).

11. A jet strikes a curved plate at its ______

a) Sides

b) Surface

c) Centre

d) Does not strike

Answer: c

Explanation: A jet strikes a curved plate at its centre. Force exerted by a jet on a stationery plate happens in three cases. The three cases are classified depending on their position. The three cases are when plate is vertical, plate is inclined and plate is curved with respect to the jet.

12. Jet propulsion of ship is less efficient than screw propeller due to_______

a) Pressure

b) Temperature

c) Frictional losses

d) Wear and tear

Answer: c

Explanation: Jet propulsion of ship is less efficient than screw propeller due to large amount of frictional losses developed in the pump and the pipeline. Thus, it is rarely used in ships.

13. Jet propulsion of ship in a very shallow water is needed to_________

a) Avoid sinking of the ship

b) Avoid damage of the propeller

c) Avoid current directions

d) Avoid surface damage

Answer: b

Explanation: Jet propulsion of ship in a very shallow water is needed to avoid damage of the propeller. Jet propulsion of ship is less efficient than screw propeller due to large amount of frictional losses developed in the pump and the pipeline.

14. A turbojet does not consist of which of the following component?

a) Compressor

b) Combustion chamber

c) Gas turbine

d) Air filter

Answer: d

Explanation: A turbojet consists of four major components for an efficient working. The four components are compressor, combustion chamber, gas turbine and a nozzle. Air filter is not used in a turbojet.

15. Which among the following is not a type of jet engine?

a) Turbojet

b) Ramjet

c) Scramjet

d) Propulsive jet

Answer: d

Explanation: A jet engine is broadly classified into four types of jet. The four types of jet are turbojet, ramjet, scramjet, and pulse jet. There isn’t anything related to the propulsive jet and thus cannot be the answer.