Hydraulics & Fluid Mechanics:
Question No. 01
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: Option C
Question No. 02
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
Answer: Option C
Question No. 03
A weir is said to be narrow-crested weir, if the width of the crest of the weir is __________ half
the height of water above the weir crest.
(A) Equal to
(B) Less than
(C) More than
(D) None of these
Answer: Option B
Question No. 04
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: Option D
Question No. 05
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
Answer: Option D
Question No. 06
The pressure of the liquid flowing through the divergent portion of a Venturimeter
(A) Remains constant
(B) Increases
(C) Decreases
(D) Depends upon mass of liquid
Answer: Option C
Question No. 07
When the Mach number is between __________ the flow is called super-sonic flow.
(A) 1 and 2.5
(B) 2.5 and 4
(C) 4 and 6
(D) 1 and 6
Answer: Option D
Question No. 08
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: Option C
Question No. 09
A vertically immersed surface is shown in the below figure. The distance of its centre of pressure
from the water surface is
(A) (bd²/12) + x̅
(B) (d²/12 ) + x̅
(C) b²/12 + x̅
(D) d²/12 + x̅
Answer: Option B
Question No. 10
The torque required to overcome viscous resistance of a collar bearing is (where R1 andR2 =
External and internal radius of collar)
A. (μπ²N/60t) × (R₁ - R₂)
B. (μπ²N/60t) × (R₁² - R₂²)
C. μπ²N/60t) × (R₁³ - R₂³)
D. (μπ²N/60t) × (R₁⁴ - R₂⁴)
Answer: Option D
Question No. 11
Steady 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) 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: Option B
Question No. 12
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: Option C
Question No. 13
In a forced vortex, the velocity of flow everywhere within the fluid is
(A) Maximum
(B) Minimum
(C) Zero
(D) Nonzero finite
Answer: Option D
Question No. 14
The depth of centre of pressure (h) for a vertically immersed surface from the liquid surface is
given by (where IG = Moment of inertia of the immersed surface about horizontal axis through its
centre of gravity, A = Area of immersed surface, and x = Depth of centre of gravity of the immersed
surface from the liquid surface)
A. (IG/Ax̅) - x̅
B. (IG/x̅) - Ax̅
C. (Ax̅/IG) + x̅
D. (IG/Ax̅) + x̅
Answer: Option D
Question No. 15
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: Option A
Question No. 16
A fluid which obeys the Newton's law of viscosity is termed as
(A) Real fluid
(B) Ideal fluid
(C) Newtonian fluid
(D) Non-Newtonian fluid
Answer: Option C
Question No. 17
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: Option D
Question No. 18
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: Option C
Question No. 19
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: Option D
Question No. 20
The value of coefficient of velocity for a sharp edged orifice __________ with the head of water.
(A) Decreases
(B) Increases
(C) Remain same
(D) None of these
Answer: Option B
Question No. 21
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: Option C
Question No. 22
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
Answer: Option A
Question No. 23
A one dimensional flow is one which
(A) Is uniform flow
(B) Is steady uniform flow
(C) Takes place in straight lines
(D) Involves zero transverse component of flow
Answer: Option D
Question No. 24
According to Manning's formula, the discharge through an open channel is (where M = Manning's
constant)
(A) A × M × m
1/2 × i2/3
(B) A × M × m
2/3 × i1/2
(C) A
1/2 × M
2/3 × m × i
(D) A
2/3 × M
1/3 × m × i
Answer: Option B
Question No. 25
Dimensions of surface tension are
(A)ML°T¯²
(B) ML°T
(C) ML r²
(D) ML²T²
Answer: Option A
Question No. 26
An opening in the side of a tank or vessel such that the liquid surface with the tank is below the
top edge of the opening, is called
(A) Weir
(B) Notch
(C) Orifice
(D) None of these
Answer: Option B
Question No. 27
The property of fluid by virtue of which it offers resistance to shear is called
(A) Surface tension
(B) Adhesion
(C) Cohesion
(D) Viscosity
Answer: Option D
Question No. 28
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: Option A
Question No. 29
A liquid compressed in cylinder has a volume of 0.04 m3
at 50 kg/cm² and a volume of 0.039 m3
at
150 kg/cm². The bulk modulus of elasticity of liquid is
(A) 400 kg/cm²
(B) 4000 kg/cm²
(C) 40 x 105 kg/cm²
(D) 40 x 106 kg/cm²
Answer: Option B
Question No. 30
The mass of 2.5 m3
of a certain liquid is 2 tonnes. Its mass density is
(A) 200 kg/m3
(B) 400 kg/m3
(C) 600 kg/m3
(D) 800 kg/m3
Answer: Option D
Question No. 31
A fluid in equilibrium can't sustain
(A) Tensile stress
(B) Compressive stress
(C) Shear stress
(D) Bending stress
Answer: Option C
Question No. 32
When a plate is immersed in a liquid parallel to the flow, it will be subjected to a pressure
__________ that if the same plate is immersed perpendicular to the flow.
(A) Less than
(B) More than
(C) Equal to
(D) None of these
Answer: Option A
Question No. 33
An object having 10 kg mass weighs 9.81 kg on a spring balance. The value of 'g' at this place is
(A) 10 m/sec²
(B) 9.81 m/sec²
(C) 9.75 m/sec²
(D) 9 m/sec
Answer: Option A
Question No. 34
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
Answer: Option D
Question No. 35
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: Option D
Question No. 36
When a cylindrical vessel containing liquid is resolved, the surface of the liquid takes the shape of
(A) A triangle
(B) A paraboloid
(C) An ellipse
(D) None of these
Answer: Option B
Question No. 37
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: Option D
Question No. 38
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: Option D
Question No. 39
The property of a fluid which enables it to resist tensile stress is known as
(A) Compressibility
(B) Surface tension
(C) Cohesion
(D) Adhesion
Answer: Option C
Question No. 40
The loss of pressure head in case of laminar flow is proportional to
(A) Velocity
(B) (Velocity)2
(C) (Velocity)3
(D) (Velocity)4 Answer: Option A
Question No. 41
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
Answer: Option A
Question No. 42
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: Option A
Question No. 43
The unit of viscosity is
(A) Metres² per sec
(B) kg-sec/metre
(C) Newton-sec per metre²
(D) Newton-sec per meter
Answer: Option B
Question No. 44
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: Option D
Question No. 45
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: Option A
Question No. 46
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: Option C
Question No. 47
A pressure of 25 m of head of water is equal to
(A) 25 kN/ m²
(B) 245 kN/ m²
(C) 2500 kN/m²
(D) 2.5 kN/ m²
Answer: Option B
Question No. 48
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: Option C
Question No. 49
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
Answer: Option B
Question No. 50
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
(B) Broad-crested weir
(C) Ogee weir
(D) Submerged weir
Answer: Option D
Question No. 51
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: Option C
Question No. 52
The increase in pressure at the outer edge of a drum of radius (r) completely filled up with liquid
A. ρ ω2 r2
B. 2ρ ω2 r2
C. ρ ω2 r2/2
D. ρ ω2 r2/4
Answer: Option C
Question No. 53
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: Option B
Question No. 54
The torque required to overcome viscous resistance of a footstep bearing is (where μ = Viscosity of the oil, N = Speed of the shaft, R = Radius of the shaft, and t = Thickness of the oil film)
A. μπ²NR/60t
B. μπ²NR²/60t
C. μπ²NR³/60t
D. μπ²NR⁴/60t
Question No. 55
Dynamic viscosity of most of the gases with rise in temperature
(A) Increases
(B) Decreases
(C) Remain unaffected
(D) Unpredictable
Answer: Option A
Question No. 56
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: Option A
Question No. 57
Center of buoyancy is the
(A) Centroid of the displaced volume of fluid
(B) Center of pressure of displaced volume
(C) Does not exist
(D) None of the above
Answer: Option A
Question No. 58
The loss of head due to viscosity for laminar flow in pipes is (where d = Diameter of pipe, l =
Length of pipe, v w = Specific
weight of the flowing liquid)
A. 4μvl/wd²
B. 8μvl/wd²
C. 16μvl/wd²
D. 32μvl/wd²
Answer: Option D
Question No. 59
For a body floating in a liquid the normal pressure exerted by the liquid acts at
(A) Bottom surface of the body
(B) C.G. of the body
(C) Metacentre
(D) All points on the surface of the body
Answer: Option D
Question No. 60
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: Option B
Question No. 61
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: Option D
Question No. 62
When a body is immersed wholly or partially in a liquid, it is lifted up by a force equal to the
weight of liquid displaced by the body. This statement is called
(A) Pascal's law
(B) Archimedes's principal
(C) Principle of floatation
(D) Bernoulli's theorem
Answer: Option B
Question No. 63
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: Option C
Question No. 64
When a tube of smaller diameter is dipped in water, the water rises in the tube with an upward
__________ surface.
(A) Concave
(B) Convex
(C) Plane
(D) None of these
Answer: Option A
Question No. 65
A piece of metal of specific gravity 7 floats in mercury of specific gravity 13.6. What fraction of its
volume is under mercury?
(A) 0.5
(B) 0.4
(C) 0.515
(D) 0.5
Answer: Option C
Question No. 66
A flow through an expanding tube at constant rate is called
(A) Steady uniform flow
(B) Steady non-uniform flow
(C) Unsteady uniform flow
(D) Unsteady non-uniform flow
Answer: Option B
Question No. 67
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: Option B
Question No. 68
The loss of head due to friction in a pipe of uniform diameter in which a viscous flow is taking
place, is (where RN = Reynold number)
(A) 1/RN
(B) 4/RN
(C) 16/RN
(D) 64/RN
Answer: Option C
Question No. 69
Practical fluids
(A) Are viscous
(B) Possess surface tension
(C) Are compressible
(D) Possess all the above properties
Answer: Option D
Question No. 70
A compound pipe of diameter d1, d2 and d3 having lengths l1, l2 and l3 is to be replaced by an
equivalent pipe of uniform diameter d and of the same length (l) as that of the compound pipe.
The size of the equivalent pipe is given by
A. l/d² = (l₁/d₁²) + (l₂/d₂²) + (l₃/d₃²)
B. l/d³ = (l₁/d₁³) + (l₂/d₂³) + (l₃/d₃³)
C. l/d⁴ = (l₁/d₁⁴) + (l₂/d₂⁴) + (l₃/d₃⁴)
D. l/d⁵ = (l₁/d₁⁵) + (l₂/d₂⁵) + (l₃/d₃⁵)
Answer: Option D
Question No. 71
The tendency of a liquid surface to contract is due to the following property
(A) Cohesion
(B) Adhesion
(C) Viscosity
(D) Surface tension
Answer: Option D
Question No. 72
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: Option D
Question No. 73
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
Answer: Option A
Question No. 74
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: Option B
Question No. 75
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
Answer: Option B
Question No. 76
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: Option A
Question No. 77
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: Option A
Question No. 78
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
Answer: Option A
Question No. 79
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: Option D
Question No. 80
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: Option C
Question No. 81
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
Answer: Option B
Question No. 82
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
Answer: Option D
Question No. 83
A tank of uniform cross-sectional area (A) containing liquid upto height (H1) has an orifice of cross-
sectional area (a) at its bottom. The time required to bring the liquid level from H1 to H2 will be
(A) 2A × d × a × 2g)
(B) 2A × d × a × 2g)
(C) 2A × - d × a × 2g)
(D) 2A × 3/2
- 3/2)/Cd × a × 2g)
Answer: Option C
Question No. 84
Gradually varied flow is
(A) Steady uniform
(B) Non-steady non-uniform
(C) Non-steady uniform
(D) Steady non-uniform
Answer: Option D
Question No. 85
The viscosity of water at 20°C is
(A) One stoke
(B) One centistoke
(C) One poise
(D) One centipoise
Answer: Option D
Question No. 86
The velocity of jet of water travelling out of opening in a tank filled with water is proportional to
(A) Head of water (h)
(B) h²
(C) V/T
(D) h/2
Answer: Option C
Question No. 87
According to Darcy's formula, the loss of head due to friction in the pipe is (where f = Darcy's
coefficient, l = Length of pipe, v = Velocity of liquid in pipe, and d = Diameter of pipe)
(A) flv²/2gd
(B) flv²/gd
(C) 3flv²/2gd
(D) 4flv²/2gd
Answer: Option D
Question No. 88
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: Option D
Question No. 89
The discharge through a convergent mouthpiece is __________ the discharge through an internal
mouthpiece of the same diameter and head of water.
(A) Equal to
(B) One-half
(C) Three fourth
(D) Double
Answer: Option D
Question No. 90
Bernoulli equation deals with the law of conservation of
(A) Mass
(B) Momentum
(C) Energy
(D) Work
Answer: Option C
Question No. 91
The depth of center of pressure of an immersed surface, inclined at an angle 'θ' with the liquid surface lies at a distance equal to __________ the center of gravity.
A. IG sin²θ/Ax̅ below
B. IG sin²θ/Ax̅ above
C. IG sinθ/Ax̅ below
D. IG sinθ/Ax̅ above
Answer: Option A
Question No. 92
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: Option B
Question No. 93
The rise of liquid along the walls of a revolving cylinder about the initial level is __________ the
depression of the liquid at the axis of rotation.
(A) Same as
(B) Less than
(C) More than
(D) None of these
Answer: Option A
Question No. 94
Hot wire anemometer is used to measure
(A) Pressure in gases
(B) Liquid discharge
(C) Pressure in liquids
(D) Gas velocities
Answer: Option D
Question No. 95
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: Option C
Question No. 96
The two important forces for a floating body are
(A) Buoyancy, gravit
(B) Buoyancy, pressure
(C) Buoyancy, inertial
(D) Inertial, gravity
Answer: Option A
Question No. 97
The kinematic viscosity of an oil (in stokes) whose specific gravity is 0.95 and viscosity 0.011 poise,
is
(A) 0.0116 stoke
(B) 0.116 stoke
(C) 0.0611 stoke
(D) 0.611 stoke
Answer: Option A
Question No. 98
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: Option D
Question No. 99
The pressure measured with the help of a pressure gauge is called
(A) Atmospheric pressure
(B) Gauge pressure
(C) Absolute pressure
(D) Mean pressure
Answer: Option B
Question No. 100
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: Option D
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