Hydraulics & Fluid Mechanics objective question and answer
Question No. 101
The power absorbed (in watts) in overcoming the viscous resistance of a footstep bearing is
(A) 1800 t
(B) 1800 t
(C) 3600 t
(D) 3600 t
Answer: Option B
Question No. 102
In order to increase sensitivity of U-tube manometer, one leg is usually inclined by angle . Sensitivity of inclined tube to sensitivity of U-tube is equal to
(A) Sin
(B) 1/Sin
(C) Cos
(D) 1/Cos
Answer: Option B
Question No. 103
The most economical section of a rectangular channel is one which has hydraulic mean depth or
hydraulic radius equal to
(A) Half the depth
(B) Half the breadth
(C) Twice the depth
(D) Twice the breadth
Answer: Option A
Question No. 104
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: Option D
Question No. 105
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
Answer: Option B
Question No. 106
Free surface of a liquid behaves like a sheet and tends to contract to smallest possible area due to
the
(A) Force of adhesion
(B) Force of cohesion
(C) Force of friction
(D) Force of diffusion
Answer: Option B
Question No. 107
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: Option D
Question No. 108
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
Answer: Option C
Question No. 109
A flow through a long pipe 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 A
Question No. 110
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: Option D
Question No. 111
The unit of dynamic viscosity in S.I. units is
(A) N-m/s2
(B) N-s/m2
(C) Poise
(D) Stoke
Answer: Option B
Question No. 112
A perfect gas
(A) Has constant viscosity
(B) Has zero viscosity
(C) Is in compressible
(D) None of the above
Answer: Option D
Question No. 113
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: Option A
Question No. 114
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: Option D
Question No. 115
One litre of water occupies a volume of
(A) 100 cm3
(B) 250 cm3
(C) 500 cm3
(D) 1000 cm3
Answer: Option A
Question No. 116
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: Option D
Question No. 117
The maximum discharge over a broad crested weir is
(A) 0.384 Cd × L × H1/2
(B) 0.384 Cd × L × H3/2
(C) 1.71 Cd × L × H1/2
(D) 1.71 Cd × L × H
3/2
Answer: Option D
Question No. 118
The ratio of absolute viscosity to mass density is known as
(A) Specific viscosity
(B) Viscosity index
(C) Kinematic viscosity
(D) Coefficient of viscosity
Answer: Option C
Question No. 119
Reynold's number is the ratio of inertia force to
(A) Pressure force
(B) Elastic force
(C) Gravity force
(D) Viscous force
Answer: Option D
Question No. 120
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: Option A
Question No. 121
In a footstep bearing, if the speed of the shaft is doubled, then the torque required to overcome
the viscous resistance will be
(A) Double
(B) Four times
(C) Eight times
(D) Sixteen times
Answer: Option A
Question No. 122
The continuity equation is connected with
(A) Open channel/pipe flow
(B) Compressibility of fluids
(C) Conservation of mass
(D) Steady/unsteady flow
Answer: Option C
Question No. 123
The most economical section of a trapezoidal channel is one which has hydraulic mean depth
equal to
(A) 1/2 × depth
(B) 1/2 × breadth
(C) 1/2 × sloping side
(D) 1/4 × (depth + breadth)
Answer: Option A
Question No. 124
The speed of sound in a ideal gas varies directly aa it's
(A) Absolute temperature
(B) Temperature
(C) Density
(D) Modulus of elasticity
Answer: Option A
Question No. 125
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: Option A
Question No. 126
Unit of surface tension is
(A) Energy/unit area
(B) Velocity/unit area
(C) Both of the above
(D) It has no units
Answer: Option A
Question No. 127
A Piezometer tube is used only for measuring
(A) Low pressure
(B) High pressure
(C) Moderate pressure
(D) Vacuum pressure
Answer: Option C
Question No. 128
The capillary rise at 20°C in a clean glass tube of 1 mm bore containing water is approximately
(A) 5 mm
(B) 10 mm
(C) 20 mm
(D) 30 mm
Answer: Option D
Question No. 129
The Cipoletti weir is a __________ weir.
(A) Rectangular
(B) Triangular
(C) Trapezoidal
(D) Circular
Answer: Option C
Question No. 130
Pressure of the order of 10" torr can be measured by
(A) Bourdon tube
(B) Pirani Gauge
(C) Micro-manometer
(D) Lonisation gauge
Answer: Option D
Question No. 131
The volume of a fluid __________ as the pressure increases.
(A) Remains same
(B) Decreases
(C) Increases
(D) None of these
Answer: Option B
Question No. 132
Buoyant force is
(A) The resultant force acting on a floating body
(B) The resultant force on a body due to the fluid surrounding it
(C) Equal to the volume of liquid displaced
(D) The force necessary to maintain equilibrium of a submerged body
Answer: Option B
Question No. 133
A flow through a long pipe at decreasing rate is called __________ uniform flow.
(A) Steady
(B) Unsteady
(C) Both A and B
(D) None of these
Answer: Option B
Question No. 134
Choose the wrong statement
(A) The center of buoyancy is located at the center of gravity of the displaced liquid
(B) For stability of a submerged body, the center of gravity of body must lie directly below the
center of buoyancy
(C) If C.G. and center of buoyancy coincide, the submerged body must lie at neutral equilibrium
for all positions
(D) All floating bodies are stable
Answer: Option D
Question No. 135
The intensity of pressure at any point, in a liquid, is __________ to the depth of liquid from the
surface.
(A) Equal
(B) Directly proportional
(C) Inversely proportional
(D) None of these
Answer: Option B
Question No. 136
True one-dimensional 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 A
Question No. 137
The discharge in an open channel corresponding to critical depth is
(A) Zero
(B) Minimum
(C) Maximum
(D) None of these
Answer: Option C
Question No. 138
A piece of wood having weight 5 kg floats in water with 60% of its volume under the liquid. The
specific gravity of wood is
(A) 0.83
(B) 0.6
(C) 0.4
(D) 0.3
Answer: Option B
Question No. 139
A pitot tube is used to measure the
(A) Velocity of flow at the required point in a pipe
(B) Pressure difference between two points in a pipe
(C) Total pressure of liquid flowing in a pipe
(D) Discharge through a pipe
Answer: Option A
Question No. 140
The total energy of each particle at various places in the case of perfect incompressible fluid
flowing in continuous stream
(A) Keeps on increasing
(B) Keeps on decreasing
(C) Remain constant
(D) May increase/decrease
Answer: Option C
Question No. 141
The critical depth meter is used to measure
(A) Velocity of flow in an open channel
(B) Depth of flow in an open channel
(C) Hydraulic jump
(D) Depth of channel
Answer: Option C
Question No. 142
Two pipe systems can be said to be equivalent, when the following quantities are same
(A) Friction loss and flow
(B) Length and diameter
(C) Flow and length
(D) Friction factor and diameter
Answer: Option A
Question No. 143
In a footstep bearing, if the radius of the shaft is doubled, then the torque required to overcome
the viscous resistance will be
(A) Double
(B) Four times
(C) Eight times
(D) Sixteen times
Answer: Option D
Question No. 144
Surface tension has the units of
(A) Newton-sec/m
(B) Newton-m/sec
(C) Newton/m
(D) Newton
Answer: Option C
Question No. 145
The value of bulk modulus of a fluid is required to determine
(A) Reynold's number
(B) Froude's number
(C) Mach number
(D) Euler's number
Answer: Option C
Question No. 146
Fluid is a substance which offers no resistance to change of
(A) Pressure
(B) Flow
(C) Shape
(D) Volume
Answer: Option C
Question No. 147
The pressure less than atmospheric pressure is known as
(A) Suction pressure
(B) Vacuum pressure
(C) Negative gauge pressure
(D) All of these
Answer: Option D
Question No. 148
The normal stress in a fluid will be constant in all directions at a point only if
(A) It is incompressible
(B) It has uniform viscosity
(C) It has zero viscosity
(D) It is at rest
Answer: Option D
Question No. 149
The power transmitted through a pipe is (where w = Specific weight in N/m3, and Q = Discharge in m3/s)
A. w × Q × H
B. w × Q × hf
C. w × Q (H - hf)
D. w × Q (H + hf)
Answer: Option C
Question No. 150
If w is the specific weight of liquid and k the depth of any point from the surface, then pressure intensity at that point will be
A. h
B. wh
C. w/h
D. h/w
Answer: Option B
Question No. 151
A compound pipe is required to be replaced by a new pipe. The two pipes are said to be
equivalent, if
(A) Length of both the pipes is same
(B) Diameter of both the pipes is same
(C) Loss of head and discharge of both the pipes is same
(D) Loss of head and velocity of flow in both the pipes is same
Answer: Option C
Question No. 152
The center of gravity of the volume of the liquid displaced by an immersed body is called
(A) Metacentre
(B) Center of pressure
(C) Center of buoyancy
(D) Center of gravity
Answer: Option C
Question No. 153
A flow is called sub-sonic, if the Mach number is
(A) Less than unity
(B) Unity
(C) Between 1 and 6
(D) More than 6
Answer: Option A
Question No. 154
Barometer 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 B
Question No. 155
The hydraulic gradient line lies over the centre line of the pipe by an amount equal to the
(A) Pressure head
(B) Velocity head
(C) Pressure head + velocity head
(D) Pressure head - velocity head
Answer: Option A
Question No. 156
The center of pressure of a surface subjected to fluid pressure is the point
(A) On the surface at which resultant pressure acts
(B) On the surface at which gravitational force acts
(C) At which all hydraulic forces meet
(D) Similar to metacentre
Answer: Option A
Question No. 157
The variation in the volume of a liquid with the variation of pressure is called its
(A) Surface tension
(B) Compressibility
(C) Capillarity
(D) Viscosity
Answer: Option B
Question No. 158
A model of torpedo is tested in a towing tank at a velocity of 25 m/sec. The prototype is expected
to attain a velocity of 5 m/sec. What model scale has been used?
(A) 1 : 5
(B) 1 : 2.5
(C) 1 : 25
(D) 1 : √5
Answer: Option A
Question No. 159
The surface tension of mercury at normal temperature is __________ that of water.
(A) Same as
(B) Lower than
(C) Higher than
(D) None of these
Answer: Option C
Question No. 160
Flow of water in a pipe about 3 metres in diameter can be measured by
(A) Orifice plate
(B) Venturimeter
(C) Rotameter
(D) Pitot tube
Answer: Option D
Question No. 161
According to Francis formula, the discharge over a rectangular weir is (where n = Number of end
contractions)
(A) (2/3) × Cd (L - nH) × √(2gh)
(B) (2/3) × Cd (L - 0.1nH) × × H^3/2
(C) (2/3) × Cd (L - nH) × × H²
(D) (2/3) × Cd (L - nH) × × H^5/2
Answer: Option B
Question No. 162
The equation of continuity holds good when the flow
(A) Is steady
(B) Is one dimensional
(C) Velocity is uniform at all the cross sections
(D) All of the above
Answer: Option D
Question No. 163
A thick liquid like syrup has a __________ viscosity than a light liquid like water.
(A) Lesser
(B) Greater
(C) Same
(D) None of these
Answer: Option B
Question No. 164
Cavitation will begin when
(A) The pressure at any location reaches an absolute pressure equal to the saturated vapour
pressure of the liquid
(B) Pressure becomes more than critical pressure
(C) Flow is increased
(D) Pressure is increased
Answer: Option A
Question No. 165
When a liquid is flowing through a pipe, the velocity of the liquid is
(A) Maximum at the centre and minimum near the walls
(B) Minimum at the centre and maximum near the walls
(C) Zero at the centre and maximum near the walls
(D) Maximum at the centre and zero near the walls
Answer: Option A
Question No. 166
Metacentric height is the distance between the metacentre and
(A) Water surface
(B) Center of pressure
(C) Center of gravity
(D) Center of buoyancy
Answer: Option C
Question No. 167
The velocity through a channel of circular section will be maximum when the depth of water is
__________ the diameter of the circular channel.
(A) 0.34 times
(B) 0.67 times
(C) 0.81 times
(D) 0.95 times
Answer: Option C
Question No. 168
Resultant pressure of the liquid in the case of an immersed body acts through
(A) Centre of gravity
(B) Centre of pressure
(C) Metacentre
(D) Centre of buoyancy
Answer: Option B
Question No. 169
A fluid is said to be ideal, if it is
(A) Incompressible
(B) Viscous and incompressible
(C) Inviscous and compressible
(D) Inviscous and incompressible
Answer: Option D
Question No. 170
In a depressed 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: Option B
Question No. 171
The value of the coefficient of compressibility for water at ordinary pressure and temperature in
kg/cm is equal to
(A) 2100
(B) 2700
(C) 10,000
(D) 21,000
Answer: Option D
Question No. 172
In one dimensional flow, the flow
(A) Is steady and uniform
(B) Takes place in straight line
(C) Takes place in curve
(D) Takes place in one direction
Answer: Option B
Question No. 173
To avoid vaporisation in the pipe line, the pipe line over the ridge is laid such that it is not more
than
(A) 2.4 m above the hydraulic gradient
(B) 6.4 m above the hydraulic gradient
(C) 10.0 m above the hydraulic gradient
(D) 5.0 above the hydraulic gradient
Answer: Option B
Question No. 174
The loss of head at exit of a pipe is (where v = Velocity of liquid in the pipe)
(A) v²/2g
(B) 0.5v²/2g
(C) 0.375v²/2g
(D) 0.75v²/2g
Answer: Option A
Question No. 175
Metacentre is the point of intersection of
(A) Vertical upward force through e.g. of body and center line of body
(B) Buoyant force and the center line of body
(C) Midpoint between e.g. and center of buoyancy
(D) All of the above
Answer: Option B
Question No. 176
The imaginary line drawn in the fluid in such a way that the tangent to any point gives the
direction of motion at that point, is known as
(A) Path line
(B) Stream line
(C) Steak line
(D) Potential line
Answer: Option B
Question No. 177
An open vessel of water is accelerated up an inclined plane. The free water surface will
(A) Be horizontal
(B) Make an angle in direction of inclination of inclined plane
(C) Make an angle in opposite direction to inclination of inclined plane
(D) Any one of above is possible
Answer: Option C
Question No. 178
The discharge over a rectangular notch is
(A) Inversely proportional to H
3/2
(B) Directly proportional to H
3/2
(C) Inversely proportional to H
5/2
(D) Directly proportional to H
5/2
Answer: Option B
Question No. 179
The flow in which each liquid particle has a definite path and their paths do not cross each other is
called
(A) One dimensional flow
(B) Streamline flow
(C) Steady flow
(D) Turbulent flow
Answer: Option B
Question No. 180
The magnitude of water hammer depends upon the
(A) Elastic properties of the pipe material
(B) Elastic properties of the liquid flowing through the pipe
(C) Speed at which the valve is closed
(D) All of the above
Answer: Option D
Question No. 181
The fluid forces considered in the Navier Stokes equation are
(A) Gravity, pressure and viscous
(B) Gravity, pressure and turbulent
(C) Pressure, viscous and turbulent
(D) Gravity, viscous and turbulent
Answer: Option A
Question No. 182
When the Venturimeter is inclined, then for a given flow it will show __________ reading.
(A) Same
(B) More
(C) Less
(D) None of these
Answer: Option A
Question No. 183
Cavitation is caused by
(A) High velocity
(B) High pressure
(C) Weak material
(D) Low pressure
Answer: Option D
Question No. 184
A vertical wall is subjected to a pressure due to one kind of liquid, on one of its sides. The total
pressure on the wall acts at a distance __________ from the liquid surface.
(A) H/3
(B) H/2
(C) 2H/3
(D) 3H/4
Answer: Option C
Question No. 185
An ideal flow of any fluid must fulfill the following
(A) Newton's law of motion
(B) Newton's law of viscosity
(C) Pascal' law
(D) Continuity equation
Answer: Option D
Question No. 186
The flow in a pipe or channel is said to be uniform when
(A) The liquid particles at all sections have the same velocities
(B) The liquid particles at different sections have different velocities
(C) The quantity of liquid flowing per second is constant
(D) Each liquid particle has a definite path
Answer: Option A
Question No. 187
Surface tension
(A) Acts in the plane of the interface normal to any line in the surface
(B) Is also known as capillarity
(C) Is a function of the curvature of the interface
(D) Decreases with fall in temperature
Answer: Option A
Question No. 188
Select the wrong statement
(A) An equivalent pipe is treated as an ordinary pipe for all calculations
(B) The length of an equivalent pipe is equal to that of a compound pipe
(C) The discharge through an equivalent pipe is equal to that of a compound pipe
(D) The diameter of an equivalent pipe is equal to that of a compound pipe
Answer: Option D
Question No. 189
Alcohol is used in manometers because
(A) It has low vapour pressure
(B) It is clearly visible
(C) It has low surface tension
(D) It can provide longer column due to low density
Answer: Option D
Question No. 190
The discharge through a wholly drowned orifice is given by (where H1 = Height of water (on the
upstream side) above the top of the orifice, H2 = Height of water (on the downstream side) above
the bottom of the orifice, and H = Difference between two water levels on either side of the
orifice)
(A) Q = Cd × gh)
(B) Q = Cd × bH2 × gh)
(C) Q = Cd × b (H2 - H1) × gh)
(D) Q = Cd × bH × 2gh)
Answer: Option C
Question No. 191
If no resistance is encountered by displacement, such a substance is known as
(A) Fluid
(B) Water
(C) Gas
(D) Ideal fluid
Answer: Option D
Question No. 192
The kinematic viscosity is the
(A) Ratio of absolute viscosity to the density of the liquid
(B) Ratio of density of the liquid to the absolute viscosity
(C) Product of absolute viscosity and density of the liquid
(D) Product of absolute viscosity and mass of the liquid
Answer: Option A
Question No. 193
Choose the correct relationship
(A) Specific gravity = gravity × density
(B) Dynamic viscosity = kinematic viscosity × density
(C) Gravity = specific gravity × density
(D) Kinematic viscosity = dynamic viscosity × density
Answer: Option B
Question No. 194
The viscosity of water is __________ than that of mercury.
(A) Higher
(B) Lower
(C) Same as
(D) None of these
Answer: Option A
Question No. 195
Surface energy per unit area of a surface is numerically equal to
(A) Atmospheric pressure
(B) Surface tension
(C) Force of adhesion
(D) Force of cohesion
Answer: Option B
Question No. 196
The specific weight of sea water is __________ that of pure water.
(A) Same as
(B) Less than
(C) More than
(D) None of these
Answer: Option C
Question No. 197
Which of the following instruments is used to measure flow on the application of Bernoulli's
theorem?
(A) Venturimeter
(B) Orifice plate
(C) Nozzle
(D) All of the above
Answer: Option D
Question No. 198
When a cylindrical vessel of radius (r) containing liquid is revolved about its vertical axis ω rad/s, then depth of parabola which the liquid assumes is
A. ω.r/2g
B. ω².r²/2g
C. ω.r/4g
D. ω².r²/4g
Answer: Option B
Question No. 199
The depth of the centre of pressure on a vertical rectangular gate 8 m wide and 6 m high, when
the water surface coincides with the top of the gate, is
(A) 2.4 m
(B) 3.0 m
(C) 4.0 m
(D) 5.0 m
Answer: Option B
Question No. 200
An internal mouthpiece is said to be running free if the length of the mouthpiece is __________
the diameter of the orifice.
(A) Less than twice
(B) More than twice
(C) Less than three times
(D) More than three times
Answer: Option C
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