Fluid Mechanics MCQ Questions & Answers
1. The celerity (velocity) of a pressure wave in a fluid is given by (where K = Bulk modulus, and ρ = Density of the fluid)
(A) K.ρ
(B) K/ρ
(C) ρ/K
(D) None of these
2. A fluid having no viscosity is known as
(A) Real fluid
(B) Ideal fluid
(C) Newtonian fluid
(D) Non-Newtonian fluid
3. In order to avoid tendency of separation at throat in a Venturimeter, the ratio of the diameter at throat to the diameter of pipe should be
(A) 1/16 to 1/8
(B) 1/8 to 1/4
(C) 1/4 to 1/3
(D) 1/3 to 1/2
4. Liquids transmit pressure equally in all the directions. This is according to
(A) Boyle’s law
(B) Archimedes principle
(C) Pascal’s law
(D) Newton’s formula
5. The discharge over a triangular notch is
(A) Inversely proportional to H3/2
(B) Directly proportional to H3/2
(C) Inversely proportional to H5/2
(D) Directly proportional to H5/2
6. A flow whose streamline is represented by a straight line, is called __________ dimensional flow.
(A) One
(B) Two
(C) Three
(D) Four
7. The body will float if the force of buoyancy is __________ the weight of the liquid displaced.
(A) Equal to
(B) Less than
(C) More than
(D) None of these
8. The density of water is 1000 kg/m3 at
(A) 0° C
(B) 0° K
(C) 4° C
(D) 20° C
9. Bulk modulus of a fluid __________ as the pressure increases.
(A) Remain same
(B) Decreases
(C) Increases
(D) None of these
10. The coefficient of viscosity may be determined by
(A) Capillary tube method
(B) Orifice type viscometer
(C) Rotating cylinder method
(D) All of these
11. According to Newton’s law of viscosity, the shear stress on a layer of a fluid is __________ to the rate of shear strain.
(A) Equal to
(B) Directly proportional
(C) Inversely proportional
(D) None of these
12. A vessel of 4 m3 contains oil which weighs 30 kN. The specific weight of the oil is
(A) 4.5 kN/m3
(B) 6 kN/m3
(C) 7.5 kN/m3
(D) 10 kN/m3
13. The increase of temperature results in
(A) Increase in viscosity of gas
(B) No changes in viscosity of liquid
(C) Decrease in viscosity of gas
(D) Decrease in viscosity of liquid
14. A manometer is used to measure
(A) Low pressure
(B) Moderate pressure
(C) High pressure
(D) Atmospheric pressure
15. Which of the following meters is not associated with viscosity?
(A) Red wood
(B) Say bolt
(C) Engler
(D) Orsat
16. The specific weight of water in S.I. units is taken as
(A) 9.81 kN/m3
(B) 9.81 × 103 N/m3
(C) 9.81 × 10-6 N/mm3
(D) Any one of these
17. 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
18. The flow in which conditions do not change with time at any point, is known as
(A) One dimensional flow
(B) Uniform flow
(C) Steady flow
(D) Turbulent flow
19. A nozzle placed at the end of a water pipe line discharges water at a
(A) Low pressure
(B) High pressure
(C) Low velocity
(D) High velocity
20. The pressure of fluid due to hammer blow is
(A) Directly proportional to density of fluid
(B) Inversely proportional to density of fluid
(C) Directly proportional to (density)1/2 of fluid
(D) Inversely proportional to (density)1/2 of fluid
21. In order to measure the flow with a Venturimeter, it is installed in
(A) Horizontal line
(B) Inclined line with flow upwards
(C) Inclined line with flow downwards
(D) Any direction and in any location
22. If mercury in a barometer is replaced by water, the height of 3.75 cm of mercury will be following cm of water
(A) 51 cm
(B) 50 cm
(C) 52 cm
(D) 52.2 cm
23. According to equation of continuity,
(A) w1a1 = w2a2
(B) w1v1 = w2v2
(C) a1v1 = a2v2
(D) a1/v1 = a2/v2
24. One poise is equal to
(A) 0.1 N-s/m2
(B) 1 N-s/m2
(C) 10 N-s/m2
(D) 100 N-s/m2
25. When a vertical wall is subjected to pressures due to liquid on both sides, the resultant pressure is the __________ of the two pressures.
(A) Sum
(B) Difference
(C) Arithmetic mean
(D) Geometric mean
26. The mercury does not wet the glass. This is due to the property of the liquid known as
(A) Cohesion
(B) Adhesion
(C) Viscosity
(D) Surface tension
27. When the pressure intensity at a point is more than the local atmospheric pressure, then the difference of these two pressures is called
(A) Gauge pressure
(B) Absolute pressure
(C) Positive gauge pressure
(D) Vacuum pressure
28. A pipe of length more than double the diameter of orifice fitted externally or internally to the orifice is called a
(A) Notch
(B) Weir
(C) Mouthpiece
(D) Nozzle
29. An open tank containing liquid is moving with an acceleration on an inclined plane. The inclination of the free surface of the liquid will be __________ to the acceleration of the tank.
(A) Equal to
(B) Directly proportional
(C) Inversely proportional
(D) None of these
30. One stoke is equal to
(A) 10-2 m2/s
(B) 10-3 m2/s
(C) 10-4 m2/s
(D) 10-6 m2/s
31. Falling drops of water become spheres due to the property of
(A) Surface tension of water
(B) Compressibility of water
(C) Capillarity of water
(D) Viscosity of water
32. The specific gravity of an oil whose specific weight is 7.85 kN/m3, is
(A) 0.8
(B) 1
(C) 1.2
(D) 1.6
33. The length of the divergent cone in a Venturimeter is __________ that of the convergent cone.
(A) Equal to
(B) Double
(C) Three to four times
(D) Five to six times
34. The stress-strain relation of the Newtonian fluid is
(A) Linear
(B) Parabolic
(C) Hyperbolic
(D) Inverse type
35. The viscosity of a liquid __________ its rate of flow through a hole in a vessel.
(A) Effects
(B) Does not effect
(C) Both A and B
(D) None of these
36. The unit of surface tension is
(A) N/m
(B) N/m2
(C) N/m3
(D) N-m
37. The units of dynamic or absolute viscosity are
(A) Metres2 per sec
(B) kg sec/meter
(C) Newton-sec per meter
(D) Newton-sec2 per meter
38. A flow in which the volume of a fluid and its density does not change during the flow is called _________ flow.
(A) Incompressible
(B) Compressible
(C) Viscous
(D) None of these
39. The weight per unit volume of a liquid at a standard temperature and pressure is called
(A) Specific weight
(B) Mass density
(C) Specific gravity
(D) None of these
40. The flow of water through the hole in the bottom of a wash basin is an example of
(A) Steady flow
(B) Uniform flow
(C) Free vortex
(D) Forced vortex
41. A flow in which the viscosity of fluid is dominating over the inertia force is called
(A) Steady flow
(B) Unsteady flow
(C) Laminar flow
(D) Turbulent flow
42. A flow whose streamline is represented by a curve, is called
(A) One-dimensional flow
(B) Two-dimensional flow
(C) Three-dimensional flow
(D) Four-dimensional flow
43. The value of coefficient of discharge is __________ the value of coefficient of velocity.
(A) Less than
(B) Same as
(C) More than
(D) None of these
44. A fluid whose viscosity does not change with the rate of deformation or shear strain is known as
(A) Real fluid
(B) Ideal fluid
(C) Newtonian fluid
(D) Non-Newtonian fluid
45. Flow occurring in a pipeline when a valve is being opened is
(A) Steady
(B) Unsteady
(C) Laminar
(D) Vortex
46. The water pressure per metre length on a vertical masonry wall of dam is (where w = Specific weight of the liquid, and H = Height of the liquid)
(A) wH/2
(B) wH
(C) wH2/2
(D) wH2/4
47. Euler’s equation in the differential form for the motion of liquids is given by
(A) dp/ρ + g.dz + v.dv = 0
(B) dp/ρ – g.dz + v.dv = 0
(C) ρ.dp + g.dz + v.dv = 0
(D) ρ.dp – g.dz + v.dv = 0
48. An open tank containing liquid is made to move from rest with a uniform acceleration. The angle 0 which the free surface of liquid makes with the horizontal is such that (where a = Horizontal acceleration of the tank, and g = Acceleration due to gravity)
(A) tanθ = a/g
(B) tanθ = 2 a/g
(C) tanθ = a/2g
(D) tanθ = a2/2g
49. A point, in a compressible flow where the velocity of fluid is zero, is called
(A) Critical point
(B) Vena contracta
(C) Stagnation point
(D) None of these
50. For very great pressures, viscosity of moss gases and liquids
(A) Remain same
(B) Increases
(C) Decreases
(D) Shows erratic behavior
51. The angle of contact in case of a liquid depends upon
(A) The nature of the liquid and the solid
(B) The material which exists above the free surface of the liquid
(C) Both of die above
(D) Any one of the above
52. Water is _________ liquid.
(A) A compressible
(B) An incompressible
(C) Both A and B
(D) None of these
53. The unit of kinematic viscosity in S. I. units is
(A) N-m/s
(B) N-s/m2
(C) m2/s
(D) N-m
54. Bernoulli’s equation is applied to
(A) Venturimeter
(B) Orifice meter
(C) Pitot tube
(D) All of these
55. Rain drops are spherical because of
(A) Viscosity
(B) Air resistance
(C) Surface tension forces
(D) Atmospheric pressure
56. General energy equation holds for
(A) Steady flow
(B) Turbulent flow
(C) Laminar flow
(D) Non-uniform flow
57. With an increase in size of tube, the rise or depression of liquid in the tube due to surface tension will
(A) Decrease
(B) Increase
(C) Remain unchanged
(D) Depend upon the characteristics of liquid
58. Gauge pressure at a point is equal to the absolute pressure __________ the atmospheric pressure.
(A) Plus
(B) Minus
(C) Divide
(D) Multiply
59. The dynamic viscosity of gases __________ with rise in temperature.
(A) Remain unaffected
(B) Increases
(C) Decreases
(D) None of these
60. The pressure of liquid at throat in a Venturimeter is __________ than that at inlet.
(A) Higher
(B) Lower
(C) Same
(D) None of these
61. The flow in which the velocity vector is identical in magnitude and direction at every point, for any given instant, is known as
(A) One dimensional flow
(B) Uniform flow
(C) Steady flow
(D) Turbulent flow
62. The specific weight of water is 1000 kg/m3
(A) At normal pressure of 760 mm
(B) At 4°C temperature
(C) At mean sea level
(D) All the above
63. If the depth of water in an open channel is greater than the critical depth, the flow is called
(A) Critical flow
(B) Turbulent flow
(C) Tranquil flow
(D) Torrential flow
64. The total pressure on the surface of a vertical sluice gate 2 m x 1 m with its top 2 m surface being 0.5 m below the water level will be
(A) 500 kg
(B) 1000 kg
(C) 1500 kg
(D) 2000 kg
65. A glass tube of small diameter (d) is dipped in fluid. The height of rise or fall in the tube given by (where w = Specific weight of liquid, α = Angle of contact of the liquid surface, and σ = Surface tension)
(A) 4wd/σ cosα
(B) σ cosα/4wd
(C) 4σ cosα/wd
(D) wd/4σ cosα
66. Two dimensional flows 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
67. The force per unit length is the unit of
(A) Surface tension
(B) Compressibility
(C) Capillarity
(D) Viscosity
68. One cubic metre of water weighs
(A) 100 liters
(B) 250 liters
(C) 500 liters
(D) 1000 liters
69. Kinematic viscosity is dependent upon
(A) Pressure
(B) Distance
(C) Density
(D) Flow
70. The Euler’s equation for the motion of liquids is based upon the assumption that
(A) The fluid is non – viscous, homogeneous and incompressible
(B) The velocity of flow is uniform over the section
(C) The flow is continuous, steady and along the stream line
(D) All of the above
71. Which of the following instrument can be used for measuring speed of a submarine moving in deep sea?
(A) Venturimeter
(B) Orifice plate
(C) Hot wire anemometer
(D) Pitot tube
72. Property of a fluid by which its own molecules are attracted is called
(A) Adhesion
(B) Cohesion
(C) Viscosity
(D) Compressibility
73. Which of the following is the unit of kinematic viscosity?
(A) Pascal
(B) Poise
(C) Stoke
(D) Faraday
74. Operation of McLeod gauge used for low pressure measurement is based on the principle of
(A) Gas law
(B) Boyle’s law
(C) Charles law
(D) Pascal’s law
75. A differential manometer is used to measure
(A) Atmospheric pressure
(B) Pressure in pipes and channels
(C) Pressure in Venturimeter
(D) Difference of pressures between two points in a pipe
76. In a venturi-flume, the flow takes place at
(A) Atmospheric pressure
(B) Gauge pressure
(C) Absolute pressure
(D) None of these
77. The normal stress is same in all directions at a point in a fluid
(A) Only when the fluid is frictionless
(B) Only when the fluid is incompressible and has zero viscosity
(C) When there is no motion of one fluid layer relative to an adjacent layer
(D) Irrespective of the motion of one fluid layer relative to an adjacent layer
78. 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 per unit length is (where w = Specific weight of liquid, and H = Height of liquid)
(A) wH
(B) wH/2
(C) wH2/2
(D) wH2/3
79. Which of the following manometer has highest sensitivity?
(A) U-tube with water
(B) Inclined U-tube
(C) U-tube with mercury
(D) Micro-manometer with water
80. Which of the following statement is wrong?
(A) A flow whose streamline is represented by a curve is called two dimensional flow.
(B) The total energy of a liquid particle is the sum of potential energy, kinetic energy and pressure energy.
(C) The length of divergent portion in a Venturimeter is equal to the convergent portion.
(D) A pitot tube is used to measure the velocity of flow at the required point in a pipe.
81. Density of water is maximum at
(A) 0° C
(B) 0° K
(C) 4° C
(D) 100° C
82. The bulk modulus of elasticity
(A) Has the dimensions of 1/pressure
(B) Increases with pressure
(C) Is large when fluid is more compressible
(D) Is independent of pressure and viscosity
83. Kinematic viscosity is equal to
(A) Dynamic viscosity/density
(B) Dynamic viscosity × density
(C) Density/dynamic viscosity
(D) 1/dynamic viscosity × density
84. The atmospheric pressure at sea level is
(A) 103 kN/m2
(B) 10.3 m of water
(C) 760 mm of mercury
(D) All of these
85. A glass tube of smaller diameter is used while performing an experiment for the capillary rise of water because
(A) It is easier to see through the glass tube
(B) Glass tube is cheaper than a metallic tube
(C) It is not possible to conduct this experiment with any other tube
(D) All of the above
86. In an isothermal atmosphere, the pressure
(A) Decreases linearly with elevation
(B) Remain constant
(C) Varies in the same way as the density
(D) Increases exponentially with elevation
87. The pressure of a liquid measured with the help of a Piezometer tube is
(A) Vacuum pressure
(B) Gauge pressure
(C) Absolute pressure
(D) Atmospheric pressure
88. If the atmospheric pressure on the surface of an oil tank (sp. gr. 0.8) is 0.2 kg/cm”, the pressure at a depth of 50 m below the oil surface will be
(A) 2 meters of water column
(B) 3 meters of water column
(C) 5 meters of water column
(D) 6 meters of water Column
89. For a perfect incompressible liquid, flowing in a continuous stream, the total energy of a particle remains the same, while the particle moves from one point to another. This statement is called
(A) Continuity equation
(B) Bernoulli’s equation
(C) Pascal’s law
(D) Archimedes’s principle
90. 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) 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 pleasure
91. At the center line of a pipe flowing under pressure where the velocity gradient is zero, the shear stress will be
(A) Minimum
(B) Maximum
(C) Zero
(D) Could be any value
92. Piezometer is used to measure
(A) Pressure in pipe, channels etc.
(B) Atmospheric pressure
(C) Very low pressures
(D) Difference of pressure between two points
93. The pressure in the air space above an oil (sp. gr. 0.8) surface in a tank is 0.1 kg/cm”. The pressure at 2.5 m below the oil surface will be
(A) 2 metres of water column
(B) 3 metres of water column
(C) 3.5 metres of water column
(D) 4 m of water column
94. The flow which neglects changes in a transverse direction is known as
(A) One dimensional flow
(B) Uniform flow
(C) Steady flow
(D) Turbulent flow
95. A moving fluid mass may be brought to a static equilibrium position, by applying an imaginary inertia force of the same magnitude as that of the accelerating force but in the opposite direction. This statement is called
(A) Pascal’s law
(B) Archimedes’s principle
(C) D-Alembert’s principle
(D) None of these
96. The mass per unit volume of a liquid at a standard temperature and pressure is called
(A) Specific weight
(B) Mass density
(C) Specific gravity
(D) None of these
97. The velocity of the liquid flowing through the divergent portion of a Venturimeter
(A) Remains constant
(B) Increases
(C) Decreases
(D) Depends upon mass of liquid
98. The volumetric change of the fluid caused by a resistance is known as
(A) Volumetric strain
(B) Volumetric index
(C) Compressibility
(D) Adhesion
99. Choose the wrong statement
(A) Fluids are capable of flowing
(B) Fluids conform to the shape of the containing vessels
(C) When in equilibrium, fluids cannot sustain tangential forces
(D) When in equilibrium, fluids can sustain shear forces
100. An orifice is said to be large, if
(A) The size of orifice is large
(B) The velocity of flow is large
(C) The available head of liquid is more than 5 times the height of orifice
(D) The available head of liquid is less than 5 times the height of orifice
101. A piece of metal of specific gravity 13.6 is placed in mercury of specific gravity 13.6, what fraction of it volume is under mercury?
(A) The metal piece will simply float over the mercury
(B) The metal piece will be immersed in mercury by half
(C) Whole of the metal piece will be immersed with its top surface just at mercury level
(D) Metal piece will sink to the bottom
102. Dynamic viscosity of most of the liquids with rise in temperature
(A) Increases
(B) Decreases
(C) Remain unaffected
(D) Unpredictable
103. Select the correct statement
(A) Local atmospheric pressure depends upon elevation of locality only
(B) Standard atmospheric pressure is the mean local atmospheric pressure a* sea level
(C) Local atmospheric pressure is always below standard atmospheric pressure
(D) A barometer reads the difference between local and standard atmospheric pressure
104. The flow in which the particles of a fluid attain such velocities that varies from point to point in magnitude and direction as well as from instant to instant, is known as
(A) One dimensional flow
(B) Uniform flow
(C) Steady flow
(D) Turbulent flow
105. The specific weight of sea water is __________ that of pure water.
(A) Same as
(B) Less than
(C) More than
(D) None of these
106. 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
107. An ideal flow of any fluid must satisfy
(A) Pascal law
(B) Newton’s law of viscosity
(C) Boundary layer theory
(D) Continuity equation
108. The height of a water column equivalent to a pressure of 0.15 MPa is
(A) 15.3 m
(B) 25.3 m
(C) 35.3 m
(D) 45.3 m
109. The ratio of specific weight of a liquid to the specific weight of pure water at a standard temperature is called
(A) Density of liquid
(B) Specific gravity of liquid
(C) Compressibility of liquid
(D) Surface tension of liquid
110. A hydraulic press has a ram of 15 cm diameter and plunger of 1.5 cm. It is required to lift a weight of 1 tonne. The force required on plunger is equal to
(A) 10 kg
(B) 100 kg
(C) 1000 kg
(D) 1 kg
111. The total head of a liquid particle in motion is equal to
(A) Pressure head + kinetic head + potential head
(B) Pressure head – (kinetic head + potential head)
(C) Potential head – (pressure head + kinetic head)
(D) Kinetic head – (pressure head + potential head)
112. The bulk modulus of elasticity with increase in pressure
(A) Increases
(B) Decreases
(C) Remain constant
(D) Increases first up to certain limit and then decreases
113. When the Venturimeter is inclined, then for a given flow it will show __________ reading.
(A) Same
(B) More
(C) Less
(D) None of these
114. Cavitation is caused by
(A) High velocity
(B) High pressure
(C) Weak material
(D) Low pressure
115. 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
116. 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
117. 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
118. 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 × bH1 × √(2gh)
(B) Q = Cd × bH2 × √(2gh)
(C) Q = Cd × b (H2 – H1) × √(2gh)
(D) Q = Cd × bH × √(2gh)
119. If no resistance is encountered by displacement, such a substance is known as
(A) Fluid
(B) Water
(C) Gas
(D) Ideal fluid
120. 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
121. 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
122. The viscosity of water is __________ than that of mercury.
(A) Higher
(B) Lower
(C) Same as
(D) None of these
123. 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
124. 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
125. 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
126. 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
127. The unit of dynamic viscosity in S.I. units is
(A) N-m/s2
(B) N-s/m2
(C) Poise
(D) Stoke
128. A perfect gas
(A) Has constant viscosity
(B) Has zero viscosity
(C) Is in compressible
(D) None of the above
129. 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
130. One liter of water occupies a volume of
(A) 100 cm3
(B) 250 cm3
(C) 500 cm3
(D) 1000 cm3
131. 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 × H3/2
132. The ratio of absolute viscosity to mass density is known as
(A) Specific viscosity
(B) Viscosity index
(C) Kinematic viscosity
(D) Coefficient of viscosity
133. Hot wire anemometer is used to measure
(A) Pressure in gases
(B) Liquid discharge
(C) Pressure in liquids
(D) Gas velocities