# 590+ Hydraulics and Fluid Mechanics Solved MCQs

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1.

## When a body is placed over a liquid, it will sink down if

A. Gravitational force is equal to the up-thrust of the liquid
B. Gravitational force is less than the up-thrust of the liquid
C. Gravitational force is more than the up-thrust of the liquid
D. None of the above
Answer» C. Gravitational force is more than the up-thrust of the liquid
2.

## The property by virtue of which a liquid opposes relative motion between its different layers is called

A. Surface tension
B. Coefficient of viscosity
C. Viscosity
D. Osmosis
3.

A. Equal to
B. Less than
C. More than
D. None of these
4.

## Euler's dimensionless number relates the following

A. Inertial force and gravity
B. Viscous force and inertial force
C. Viscous force and buoyancy force
D. Pressure force and inertial force
Answer» D. Pressure force and inertial force
5.

## When a body floating in a liquid, is displaced slightly, it oscillates about

A. C.G. of body
B. Center of pressure
C. Center of buoyancy
D. Metacentre
6.

A. 1 and 2.5
B. 2.5 and 4
C. 4 and 6
D. 1 and 6
7.

## In an immersed body, centre of pressure is

A. At the centre of gravity
B. Above the centre of gravity
C. Below be centre of gravity
D. Could be above or below e.g. depending on density of body and liquid
Answer» C. Below be centre of gravity
8.

A. The direction and magnitude of the velocity at all points are identical
B. The velocity of successive fluid particles, at any point, is the same at successive periods of time
C. The magnitude and direction of the velocity do not change from point to point in the fluid
D. The fluid particles move in plane or parallel planes and the streamline patterns are identical in each plane
Answer» B. The velocity of successive fluid particles, at any point, is the same at successive periods of time
9.

## A flow is called super-sonic if the

A. Velocity of flow is very high
B. Discharge is difficult to measure
C. Mach number is between 1 and 6
D. None of these
Answer» C. Mach number is between 1 and 6
10.

## In a forced vortex, the velocity of flow everywhere within the fluid is

A. Maximum
B. Minimum
C. Zero
D. Nonzero finite
11.

## Mach number is significant in

A. Supersonics, as with projectiles and jet propulsion
B. Full immersion or completely enclosed flow, as with pipes, aircraft wings, nozzles etc.
C. Simultaneous motion through two fluids where there is a surface of discontinuity, gravity force, and wave making effects, as with ship's hulls
D. All of the above
Answer» A. Supersonics, as with projectiles and jet propulsion
12.

## In order that flow takes place between two points in a pipeline, the differential pressure between these points must be more than

A. Frictional force
B. Viscosity
C. Surface friction
D. All of the above
Answer» D. All of the above
13.

## The error in discharge (dQ/Q) to the error in measurement of head (dH/H) over a triangular notch is given by

A. dQ/Q = 3/2 × (dH/H)
B. dQ/Q = 2 × (dH/H)
C. dQ/Q = 5/2 × (dH/H)
D. dQ/Q = 3 × (dH/H)
Answer» C. dQ/Q = 5/2 × (dH/H)
14.

## For similarity, in addition to models being geometrically similar to prototype, the following in both cases should also be equal

A. Ratio of inertial force to force due to viscosity
B. Ratio of inertial force to force due to gravitation
C. Ratio of inertial force to force due to surface tension
D. All the four ratios of inertial force to force due to viscosity, gravitation, surface tension, and elasticity
Answer» D. All the four ratios of inertial force to force due to viscosity, gravitation, surface tension, and elasticity
15.

A. Decreases
B. Increases
C. Remain same
D. None of these
16.

## If cohesion between molecules of a fluid is greater than adhesion between fluid and glass, then the free level of fluid in a dipped glass tube will be

A. Higher than the surface of liquid
B. The same as the surface of liquid
C. Lower than the surface of liquid
D. Unpredictable
Answer» C. Lower than the surface of liquid
17.

## The ratio of the inertia force to the __________ is called Euler's number.

A. Pressure force
B. Elastic force
C. Surface tension force
D. Viscous force
18.

## A one dimensional flow is one which

A. Is uniform flow
C. Takes place in straight lines
D. Involves zero transverse component of flow
Answer» D. Involves zero transverse component of flow
19.

## According to Manning's formula, the discharge through an open channel is (where M = Manning's constant)

A. A × M × m1/2 × i2/3
B. A × M × m2/3 × i1/2
C. A1/2 × M 2/3 × m × i
D. A2/3 × M1/3 × m × i
Answer» B. A × M × m2/3 × i1/2
20.

A. Weir
B. Notch
C. Orifice
D. None of these
21.

## The property of fluid by virtue of which it offers resistance to shear is called

A. Surface tension
C. Cohesion
D. Viscosity
22.

## Coefficient of velocity is defined as the ratio of

A. Actual velocity of jet at vena contracta to the theoretical velocity
B. Area of jet at vena contracta to the area of orifice
C. Actual discharge through an orifice to the theoretical discharge
D. None of the above
Answer» A. Actual velocity of jet at vena contracta to the theoretical velocity
23.

A. 200 kg/m3
B. 400 kg/m3
C. 600 kg/m3
D. 800 kg/m3
24.

## A fluid in equilibrium can't sustain

A. Tensile stress
B. Compressive stress
C. Shear stress
D. Bending stress
25.

A. Less than
B. More than
C. Equal to
D. None of these
26.

A. 10 m/sec²
B. 9.81 m/sec²
C. 9.75 m/sec²
D. 9 m/sec
27.

## A flow is called hyper-sonic, if the Mach number is

A. Less than unity
B. Unity
C. Between 1 and 6
D. None of these
28.

## Liquids

A. Cannot be compressed
B. Occupy definite volume
C. Are not affected by change in pressure and temperature
D. None of the above
Answer» D. None of the above
29.

A. A triangle
B. A paraboloid
C. An ellipse
D. None of these
30.

## Fluid is a substance that

A. Cannot be subjected to shear forces
B. Always expands until it fills any container
C. Has the same shear stress at a point regardless of its motion
D. Cannot remain at rest under action of any shear force
Answer» D. Cannot remain at rest under action of any shear force
31.

## The force exerted by a moving fluid on an immersed body is directly proportional to the rate of change of momentum due to the presence of the body. This statement is called

A. Newton's law of motion
B. Newton's law of cooling
C. Newton's law of viscosity
D. Newton's law of resistance
Answer» D. Newton's law of resistance
32.

## The property of a fluid which enables it to resist tensile stress is known as

A. Compressibility
B. Surface tension
C. Cohesion
33.

A. Velocity
B. (Velocity)2
C. (Velocity)3
D. (Velocity)4
34.

## The surface tension of mercury at normal temperature compared to that of water is

A. More
B. Less
C. Same
D. More or less depending on size of glass tube
35.

## An air vessel is provided at the summit in a siphon to

A. Avoid interruption in the flow
B. Increase discharge
C. Increase velocity
D. Maintain pressure difference
Answer» A. Avoid interruption in the flow
36.

## The unit of viscosity is

A. Metres² per sec
B. kg-sec/metre
C. Newton-sec per metre²
D. Newton-sec per meter
37.

## Select the correct statement

A. Weber's number is the ratio of inertia force to elastic force.
B. Weber's number is the ratio of gravity force to surface tension force.
C. Weber's number is the ratio of viscous force to pressure force.
D. Weber's number is the ratio of inertia force to surface tension force.
Answer» D. Weber's number is the ratio of inertia force to surface tension force.
38.

## Choose the wrong statement. Alcohol is used in manometer, because

A. Its vapour pressure is low
B. It provides suitable meniscus for the inclined tube
C. Its density is less
D. It provides longer length for a given pressure difference
Answer» A. Its vapour pressure is low
39.

## When a tank containing liquid moves with an acceleration in the horizontal direction, then the free surface of the liquid

A. Remains horizontal
B. Becomes curved
C. Falls on the front end
D. Falls on the back end
Answer» C. Falls on the front end
40.

A. 25 kN/ m²
B. 245 kN/ m²
C. 2500 kN/m²
D. 2.5 kN/ m²
41.

## The hammer blow in pipes occurs when

A. There is excessive leakage in the pipe
B. The pipe bursts under high pressure of fluid
C. The flow of fluid through the pipe is suddenly brought to rest by closing of the valve
D. The flow of fluid through the pipe is gradually brought to rest by closing of the valve
Answer» C. The flow of fluid through the pipe is suddenly brought to rest by closing of the valve
42.

## The resultant upward pressure of the fluid on an immersed body is called

A. Up-thrust
B. Buoyancy
C. Center of pressure
D. All the above are correct
43.

## When the water level on the downstream side of a weir is above the top surface of a weir, the weir is known as

A. Narrow-crested weir
C. Ogee weir
D. Submerged weir
44.

## If the surface of liquid is convex, men

A. Cohesion pressure is negligible
B. Cohesion pressure is decreased
C. Cohesion pressure is increased
D. There is no cohesion pressure
Answer» C. Cohesion pressure is increased
45.

## The atmospheric pressure with rise in altitude decreases

A. Linearly
B. First slowly and then steeply
C. First steeply and then gradually
D. Unpredictable
Answer» B. First slowly and then steeply
46.

## Dynamic viscosity of most of the gases with rise in temperature

A. Increases
B. Decreases
C. Remain unaffected
D. Unpredictable
47.

## According to Bernoulli's equation

A. Z + p/w + v²/2g = constant
B. Z + p/w - v²/2g = constant
C. Z - p/w + v²/2g = constant
D. Z - p/w - v²/2g = constant
Answer» A. Z + p/w + v²/2g = constant
48.

## Newton's law of viscosity is a relationship between

A. Pressure, velocity and temperature
B. Shear stress and rate of shear strain
C. Shear stress and velocity
D. Rate of shear strain and temperature
Answer» B. Shear stress and rate of shear strain
49.

## Differential manometer is used to measure

A. Pressure in pipes, channels etc.
B. Atmospheric pressure
C. Very low pressure
D. Difference of pressure between two points
Answer» D. Difference of pressure between two points
50.

## Non uniform flow occurs when

A. The direction and magnitude of the velocity at all points are identical
B. The velocity of successive fluid particles, at any point, is the same at successive periods of time
C. Velocity, depth, pressure, etc. change from point to point in the fluid flow.
D. The fluid particles move in plane or parallel planes and the streamline patterns are identical in each plane
Answer» C. Velocity, depth, pressure, etc. change from point to point in the fluid flow.
51.

A. 0.5
B. 0.4
C. 0.515
D. 0.5
52.

53.

## Reynolds number is significant in

A. Supersonics, as with projectile and jet propulsion
B. Full immersion or completely enclosed flow, as with pipes, aircraft wings, nozzles etc.
C. Simultaneous motion through two fluids where there is a surface of discontinuity, gravity forces, and wave making effect, as with ship's hulls
D. All of the above
Answer» B. Full immersion or completely enclosed flow, as with pipes, aircraft wings, nozzles etc.
54.

A. 1/RN
B. 4/RN
C. 16/RN
D. 64/RN
55.

## The tendency of a liquid surface to contract is due to the following property

A. Cohesion
C. Viscosity
D. Surface tension
56.

## The Newton's law of resistance is based on the assumption that the

A. Planes of the body are completely smooth
B. Space around the body is completely filled with the fluid
C. Fluid particles do not exert any influence on one another
D. All of the above
Answer» D. All of the above
57.

## For manometer, a better liquid combination is one having

A. Higher surface tension
B. Lower surface tension
C. Surface tension is no criterion
D. High density and viscosity
58.

## The flow in a pipe is neither laminar nor turbulent when Reynold number is

A. Less than 2000
B. Between 2000 and 2800
C. More than 2800
D. None of these
Answer» B. Between 2000 and 2800
59.

## The point in the immersed body through which the resultant pressure of the liquid may be taken to act is known as

A. Meta center
B. Center of pressure
C. Center of buoyancy
D. Center of gravity
60.

## Stoke is the unit of

A. Kinematic viscosity in C. G. S. units
B. Kinematic viscosity in M. K. S. units
C. Dynamic viscosity in M. K. S. units
D. Dynamic viscosity in S. I. units
Answer» A. Kinematic viscosity in C. G. S. units
61.

## The vapour pressure over the concave surface is

A. Less man the vapour pressure over the plane surface
B. Equal to the vapour pressure over the plane surface
C. Greater than the vapour pressure over the plane surface
D. Zero
Answer» A. Less man the vapour pressure over the plane surface
62.

## The velocity at which the flow changes from laminar flow to turbulent flow is called

A. Critical velocity
B. Velocity of approach
C. Sub-sonic velocity
D. Super-sonic velocity
63.

## Mercury is often used in barometer because

A. It is the best liquid
B. The height of barometer will be less
C. Its vapour pressure is so low that it may be neglected
D. Both (B) and (C)
Answer» D. Both (B) and (C)
64.

## A vertical wall is subjected to a pressure due to one kind of liquid, on one of its sides. Which of the following statement is correct?

A. The pressure on the wall at the liquid level is minimum
B. The pressure on the bottom of the wall is maximum
C. The pressure on the wall at the liquid level is zero, and on the bottom of the wall is maximum
D. The pressure on the bottom of the wall is zero
Answer» C. The pressure on the wall at the liquid level is zero, and on the bottom of the wall is maximum
65.

## Center of pressure compared to e.g. is

A. Above it
B. Below it
C. At same point
D. Above or below depending on area of body
66.

## The centre of gravity of the volume of the liquid displaced by an immersed body is called

A. Centre of gravity
B. Centre of pressure
C. Metacentre
D. Centre of buoyancy
67.

68.

## The viscosity of water at 20°C is

A. One stoke
B. One centistoke
C. One poise
D. One centipoise
69.

B.
C. V/T
D. h/2
70.

A. flv²/2gd
B. flv²/gd
C. 3flv²/2gd
D. 4flv²/2gd
71.

## According to Bernoulli's equation for steady ideal fluid flow

A. Principle of conservation of mass holds
B. Velocity and pressure are inversely proportional
C. Total energy is constant throughout
D. The energy is constant along a streamline but may vary across streamlines
Answer» D. The energy is constant along a streamline but may vary across streamlines
72.

A. Equal to
B. One-half
C. Three fourth
D. Double
73.

A. Mass
B. Momentum
C. Energy
D. Work
74.

## Principle of similitude forms the basis of

A. Comparing two identical equipments
B. Designing models so that the result can be converted to prototypes
C. Comparing similarity between design and actual equipment
D. Hydraulic designs
Answer» B. Designing models so that the result can be converted to prototypes
75.

A. Same as
B. Less than
C. More than
D. None of these
76.

## Hot wire anemometer is used to measure

A. Pressure in gases
B. Liquid discharge
C. Pressure in liquids
D. Gas velocities
77.

## Venturimeter is used to

A. Measure the velocity of a flowing liquid
B. Measure the pressure of a flowing liquid
C. Measure the discharge of liquid flowing in a pipe
D. Measure the pressure difference of liquid flowing between two points in a pipe line
Answer» C. Measure the discharge of liquid flowing in a pipe
78.

## According to the principle of buoyancy a body totally or partially immersed in a fluid will be lifted up by a force equal to

A. The weight of the body
B. More than the weight of the body
C. Less than the weight of the body
D. Weight of the fluid displaced by the body
Answer» D. Weight of the fluid displaced by the body
79.

## The pressure measured with the help of a pressure gauge is called

A. Atmospheric pressure
B. Gauge pressure
C. Absolute pressure
D. Mean pressure
80.

## The total pressure force on a plane area is equal to the area multiplied by the intensity of pressure at the Centroid, if

A. The area is horizontal
B. The area is vertical
C. The area is inclined
D. All of the above
Answer» D. All of the above
81.

## The most economical section of a rectangular channel is one which has hydraulic mean depth or hydraulic radius equal to

A. Half the depth
C. Twice the depth
82.

## Capillary action is due to the

A. Surface tension
B. Cohesion of the liquid
C. Adhesion of the liquid molecules and the molecules on the surface of a solid
D. All of the above
Answer» D. All of the above
83.

## The intensity of pressure on an immersed surface __________ with the increase in depth.

A. Does not change
B. Increases
C. Decreases
D. None of these
84.

## Which of the following statement is correct?

A. In a compressible flow, the volume of the flowing liquid changes during the flow
B. A flow, in which the volume of the flowing liquid does not change, is called incompressible flow
C. When the particles rotate about their own axes while flowing, the flow is said to be rotational flow
D. All of the above
Answer» D. All of the above
85.

## A bucket of water is hanging from a spring balance. An iron piece is suspended into water without touching sides of bucket from another support. The spring balance reading will

A. Increase
B. Decrease
C. Remain same
D. Increase/decrease depending on depth of immersion
86.

87.

## Choose the wrong statement

A. Viscosity of a fluid is that property which determines the amount of its resistance to a shearing force
B. Viscosity is due primarily to interaction between fluid molecules
C. Viscosity of liquids decreases with increase in temperature
D. Viscosity of liquids is appreciably affected by change in pressure
Answer» D. Viscosity of liquids is appreciably affected by change in pressure
88.

A. N-m/s2
B. N-s/m2
C. Poise
D. Stoke
89.

## A perfect gas

A. Has constant viscosity
B. Has zero viscosity
C. Is in compressible
D. None of the above
Answer» D. None of the above
90.

## In a free nappe,

A. The pressure below the nappe is atmospheric
B. The pressure below the nappe is negative
C. The pressure above the nappe is atmospheric
D. The pressure above the nappe is negative
Answer» A. The pressure below the nappe is atmospheric
91.

## In a static fluid

A. Resistance to shear stress is small
B. Fluid pressure is zero
C. Linear deformation is small
D. Only normal stresses can exist
Answer» D. Only normal stresses can exist
92.

A. 1000 cm3
B. 250 cm3
C. 500 cm3
D. 100 cm3
93.

## A balloon lifting in air follows the following principle

A. Law of gravitation
B. Archimedes principle
C. Principle of buoyancy
D. All of the above
Answer» D. All of the above
94.

## The ratio of absolute viscosity to mass density is known as

A. Specific viscosity
B. Viscosity index
C. Kinematic viscosity
D. Coefficient of viscosity
95.

## Reynold's number is the ratio of inertia force to

A. Pressure force
B. Elastic force
C. Gravity force
D. Viscous force
96.

## Metacentric height is given as the distance between

A. The center of gravity of the body and the metacentre
B. The center of gravity of the body and the center of buoyancy
C. The center of gravity of the body and the center of pressure
D. Center of buoyancy and metacentre
Answer» A. The center of gravity of the body and the metacentre
97.

A. Double
B. Four times
C. Eight times
D. Sixteen times
98.

## The continuity equation is connected with

A. Open channel/pipe flow
B. Compressibility of fluids
C. Conservation of mass
99.

## The most economical section of a trapezoidal channel is one which has hydraulic mean depth equal to

A. 1/2 × depth
C. 1/2 × sloping side
D. 1/4 × (depth + breadth)
100.

## The absolute pressure is equal to

A. Gauge pressure + atmospheric pressure
B. Gauge pressure - atmospheric pressure
C. Atmospheric pressure - gauge pressure
D. Gauge pressure - vacuum pressure
Answer» A. Gauge pressure + atmospheric pressure