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Fluid Mechanics MCQ Questions & Answers

Fluid Mechanics MCQs : This section focuses on the "Fluid Mechanics". These Multiple Choice Questions (MCQs) should be practiced to improve the Fluid Mechanics skills required for various interviews (campus interview, walk-in interview, company interview), placement, entrance exam and other competitive examinations.




Question 1

_____ is a mechanical gadget used to prevent leaks.

A. Hydrogen fitting
B. Stuffing Box
C. Mechanical Box
D. None of the mentioned

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Question 2

Shear stress in a fluid flowing in a round pipe

A. varies parabolically across the cross-section.
B. remains constant over the cross-section.
C. is zero at the centre and varies linearly with the radius.
D. is zero at the wall and increases linearly to the centre.

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Question 3

In food industry, chlorine line is painted _____ and hydrogen line is painted _____

A. Yellow, black
B. Green, blue
C. Orange, red
D. Yellow, red

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Question 4

Which of the following is not concerned with the fluid-particle interaction ?

A. Drag co-efficient
B. Froude number
C. Galileo number
D. Weber number

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Question 5

Molten soap mass is transported by a __________ pump.

A. diaphragm
B. reciprocating
C. gear
D. centrifugal

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Question 6

The maximum delivery pressure of compressors can be upto __________ atmospheres.

A. 10
B. 100
C. 250
D. 1000

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Question 7

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

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Question 8

For the transfer of solution of thick slurry, the pump used is a __________ pump.

A. reciprocating
B. gear
C. diaphragm
D. centrifugal

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Question 9

A Bingham fluid of viscosity μ = 10 Pa.s and yield stress, τ0 = 10 KPa, is shared between flat parallel plates separated by a distance of 10-3 m. The top plate is moving with a velocity of 1 m/s. The shear stress on the plate is

A. 10 KPa
B. 20 KPa
C. 30 KPa
D. 40 KPa

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Question 10

In Bernoulli's equation, the friction correction factor is added to the LHS and the energy contributed by the pump is written on the RHS.

A. TRUE
B. FALSE

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Question 11

Which of the following is untrue about non-return valves?

A. They're also called foot valves as they're present at the foot of centrifugal pumps to prevent priming
B. They prevent flow in the opposite direction even if the pressure increases in the opposite direction
C. All of the mentioned
D. None of the mentioned

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Question 12

The fluid in which the shearing stress within it is proportional to the velocity gradient across the sheared section, is called a __________ fluid.

A. Bingham
B. Newtonion
C. perfect
D. none of these

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Question 13

Statement 1: Reynolds number is the ratio of viscous force to Inertial Force.

A. True, False
B. True, True
C. False, False
D. False, True

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Question 14

Pick out the wrong statement.

A. Momentum transfer in laminar flow results from veclocity gradient.
B. A fluid in equilibrium is not free from shear stress.
C. The viscosity of a non-Newtonion fluid is a function of temperature only.
D. both (b) and (c)

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Question 15

Statement 1: Diaphragm pumps can handle corrosive material and do not have leakage problems, but, they only vibrate hence the output is low.

A. True, negative displacement pump
B. True, positive displacement pump
C. False, negative displacement pump
D. False, positive displacement pump

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Question 16

Brownian movement is prominent in the particle size range of __________ microns in case of settling of a particle in a fluid.

A. 2 to 3
B. 0.01 to 0.10
C. 200 to 300
D. 100 to 1000

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Question 17

A particle A of diameter 10 microns settles in an oil of specific gravity 0.9 and viscosity 10 poise under Stoke's law. A particle B with diameter 20 microns settling in the same oil will have a settling velocity

A. same as that of A.
B. one fourth as that of A.
C. twice as that of A.
D. four times as that of A.

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Question 18

For Laminar flow through a packed bed, the pressure drop is proportional to (Vs is the superficial liquid velocity and Dp is the particle diameter)

A. Vs/Dp2
B. Vs2/Dp2
C. Vs2/Dp3
D. Vs/Dp3

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Question 19

Schedule number of a pipe, which is a measure of its wall thickness, is given by

A. 1000 P'/S
B. 100 P'/S
C. 1000 S/P'
D. 10000 P'/S

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Question 20

The normal stress is the same in all directions at a point in a fluid, when the fluid is

A. non-viscous.
B. incompressible.
C. both (a) and (b).
D. having no motion of one fluid layer relative to the other.

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Question 21

With increasing flow rate, the hydraulic efficiency of a centrifugal pump

A. monotonically decreases.
B. decreases and then increases.
C. remains constant.
D. increases and then decreases.

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Question 22

The energy loss due to the friction at the walls of a pipe is called _____

A. Kinetic friction
B. Skin friction
C. Static friction
D. None of the mentioned

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Question 23

Which of the following is true about Centrifugal pumps?

A. It's suitable for corrosive and toxic fluids
B. It has a high pressure head
C. Priming is not needed
D. None of the mentioned

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Question 24

The fluid property, due to which, mercury does not wet the glass is

A. surface tension
B. viscosity
C. cohesion
D. adhesion

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Question 25

Water hammer in a pipeline results from the

A. bursting of pipelines due to closure by a valve.
B. rapid pressure change due to a rapid change in the rate of flow.
C. pressure increase due to closure of a valve resulting in decrease in rate of flow.
D. none of these.

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Question 26

Dimension of surface tension is(where, F = force, L = length)

A. FL-1
B. F-1 . L
C. F.L-2
D. F-2 . L

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Question 27

Which of the following pumps is this pump- It has no rotating or reciprocating parts involved. No leakage. Air/gas used to impart energy.

A. Piston pump
B. Diaphragm pump
C. Gear pump
D. Air-lift pump

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Question 28

Laminar flow of a Newtonion fluid ceases to exist, when the Reynolds number exceeds

A. 4000
B. 2100
C. 1500
D. 3000

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Question 29

Which of the following is not a dimension-less parameter ?

A. Euler number
B. Specific gravity
C. Fanning friction factor
D. None of these

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Question 30

When the momentum of one fluid is used for moving another fluid, such a device is called a/an

A. jet pump
B. blower
C. acid egg
D. none of these

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Question 31

Drain pipes are present to remove _____

A. Waste
B. Urea
C. Condensate
D. None of the mentioned

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Question 32

In case of hydraulically smooth pipe, the resistance to flow depends only on the Reynolds number, whereas for a hydraulically rough pipe, the resistance to flow is governed by the relative roughness. Two pipes are said to have the same hydraulic roughness, when they have equal values of

A. relative roughness.
B. absolute roughness.
C. friction co-efficient for flows at equal Reynold number.
D. all (a), (b) & (c).

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Question 33

Most commonly used joint in the underground pipe lines is the

A. sleevejoint
B. coupling
C. flange
D. expansion joint

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Question 34

The pitot static tube does not measure the __________ pressure.

A. static
B. total
C. difference in static & dynamic
D. all (a), (b) and (c)

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Question 35

All pipes of a particular nominal size have the same

A. inside diameter
B. outside diameter
C. thickness
D. none of these

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Question 36

The drag co-efficient for a bacterium moving in water at 1 mm/s, will be of the following order of magnitude (assume size of the bacterium to be 1 micron and kinematic viscosity of water to be 10-6m2/s).

A. 24000
B. 24
C. 0.24
D. 0.44

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Question 37

The net positive suction head (NPSH) of a centrifugal pump is defined as the sum of the velocity head and the pressure head at the

A. discharge.
B. suction.
C. suction minus vapor pressure of the liquid at suction temperature.
D. discharge minus vapor pressure of the liquid at the discharge temperature.

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Question 38

If the discharge of a centrifugal pump is throttled, then its suction lift

A. increases
B. decreases
C. remains unchanged
D. data insufficient to predict

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Question 39

In fluid flow, cavitation is caused, if the

A. fluid velocity decreases to zero.
B. total energy decreases.
C. both (a) and (b).
D. flow pressure approaches its vapor pressure at the prevailing temperature.

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Question 40

The terminal velocity of a small sphere settling in a viscous fluid varies as the

A. first power of its dimeter.
B. inverse of the fluid viscosity.
C. inverse square of the diameter.
D. square of the difference in specific weights of solid & fluid.

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Question 41

For a particle settling in water at its terminal settling velocity, which of the following is true ?

A. Buoyancy = weight + drag
B. Weight = buoyancy + drag
C. Drag = buoyancy + weight
D. Drag = weight

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Question 42

The velocity profile for turbulent flow through a closed conduit is

A. logarithmic
B. parabolic
C. hyperbolic
D. linear

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Question 43

Pressure drag does not depend upon the

A. roughness of surface of the body.
B. pressure of main flow only.
C. length of the body in flow direction.
D. all (a), (b) and (c)

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Question 44

The ratio of the depth of flow to the hydraulic radius for the most economical trapezoidal section, in open channel flow is

A. 0.5
B. 1
C. 1.5
D. 2

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Question 45

Power loss in an orificemeter is __________ that in a venturimeter.

A. less than
B. same as
C. more than
D. data insufficient, cannot be predicted

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Question 46

What is the normal range of exit cone angle of a venturimeter ?

A. 2 to 5
B. 7 to 15
C. 15 to 25
D. >25

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Question 47

Co-efficient of velocity is __________ the coefficient of discharge.

A. less than
B. more than
C. equal to
D. not related to

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Question 48

At high Reynolds number

A. inertial forces control and viscous forces are unimportant.
B. viscous forces predominate.
C. inertial forces are unimportant and viscous forces control.
D. none of these.

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Question 49

Pick out the correct statement.

A. A forced vortex occurs when fluid rotates as a solid about an axis.
B. In laminar flow, Newton's law of viscosity does not apply.
C. A free vortex occurs, when fluidrotates as a solid.
D. In turbulent flow, there are neither cross-currents nor eddies.

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Question 50

Hydraulic mean depth (Dm) for a circular pipe of diameter 'D' flowing full is 0.25 D. For a circular channel, at Dm = 0.3 D, gives the condition for the maximum

A. flow rate
B. mean velocity
C. both 'a' & 'b'
D. neither 'a' nor 'b'

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Question 51

The resistance wire used in a hot wire anemometer for conducting electrical current is made of

A. copper
B. tungsten
C. chromium
D. aluminium

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Question 52

The dimension of dynamic viscosity is

A. ML-1T-1
B. L2T-1
C. LT-2
D. ML-1T-2

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Question 53

The terminal velocity of a particle moving through a fluid varies as dpn. What is the value of n' for Newton's law regime ?

A. 0.5
B. 1
C. 1.5
D. 3

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Question 54

Which of the following is true about Rotary pumps?

A. These consist of gear pumps which create high pressures
B. In internal gear pumps, a pinion gear is driven by a motor which is eccentric and the ring gear is co-axial and is driven by the pinion gear
C. In Spur gears, vacuum created allows liquid to flow from suction to delivery line
D. All of the mentioned

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Question 55

Nominal size of the discharge pipe of a pump is usually __________ the nominal size of the inlet pipe.

A. smaller than
B. larger than
C. same as
D. twice

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Question 56

__________ pumps are axial flow pumps.

A. Turbine
B. Propeller
C. Diffuser
D. none of these

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Question 57

Which correction of the orifice meter is corrected in the venturimeter?

A. The eddies are not formed as the entrance to the downstream is not very big as compared to the vena contracta
B. The throat diameter can be changed
C. All of the mentioned
D. None of the mentioned

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Question 58

Dimension of absolute viscosity is

A. ML-1T-1
B. MLT-1
C. ML-1T
D. MLT

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Question 59

In a rota meter _________ force is directly proportional to _____ of the fluid.

A. Buoyancy, Linear Velocity
B. Gravitational, Volumetric flow rate
C. Gravitational, Linear Velocity
D. Buoyancy, Volumetric flow rate

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Question 60

Pipes are described in the form of _____

A. None of the mentioned
B. Formation Number
C. All of the mentioned
D. Schedule Number

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Question 61

Foot valves provided in pumps are __________ valves.

A. relief
B. three/four way
C. pressure reducing
D. directional control

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Question 62

Which of the following denotes the effect of compressibility in fluid flow ?

A. Weber number
B. Mach number
C. Euler number
D. Reynolds number

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Question 63

Which of the following is true about On-Off Control?

A. On-Off valves are called Plug Cocks
B. The size of the valve path is as big as the pipe itself
C. Pressure drop in these is the least compared to all other valves
D. All of the mentioned

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Question 64

What is Kinetic Energy Factor in the Bernoulli's equation?

A. It is because friction varies
B. It is because friction stays constant
C. It is because the velocity in every layer varies and only the average velocity is accounted hence a correction factor is a need
D. None of the mentioned

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Question 65

The head loss in turbulent flow in a pipe varies

A. as velocity
B. as (velocity)2
C. inversely as the square of diameter
D. inversely as the velocity

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Question 66

Maximum theoretical suction lift for water at 15°C by a centrifugal pump is 34 ft. The same for water at 90°C will be __________ ft.

A. 40
B. 34
C. 8
D. 37

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Question 67

Head developed by a centrifugal pump depends on its

A. speed
B. impeller diameter
C. both (a) and (b)
D. neither (a) nor (b)

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