fluid mechanics MCQs – Page 2

Practise focused fluid mechanics questions with marked answers for exam preparation and subject revision.

fluid mechanics Mcqs
51. A valve is suddenly closed in a water main in wl.ich the velocity is 1 m/sec and velocity of pressure wave is 981 m/ sec. The inertia head at the valve will be________________?
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A. 1 m

B. none of the above

C. 10m

D. 100m
52. A right circular cylinder open at the top is filled with liquid and rotated about its vertical axis at such a speed that half the liquid spills out, then the pressure intensity at the center of bottom is___________________?
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A. one-half its value when cylinder was full

B. cannot be predicted from the given data

C. one-fourth its value when cylinder was full

D. zero
53. The shear stress distribution for a fluid flowing in between the parallel plates, both at rest, is_______________?
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A. constant over the cross section

B. parabolic distribution across the section

C. zero at plates and increases linearly to midpoint

D. zero at the mid plane and varies linearly with distance from mid plane
54. If x is the distance from leading edge, then the boundary layer thickness in laminar flow varies as________________?
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A. x/7

B. x

C. x

D. x

55. Size of a venturimeter is specified by________________?
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A. pipe diameter

B. throat diameter

C. angle of diverging section

D. both pipe diameter as well as throat diameter

56. Select the correct statement?
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A. The friction factor decreases with time

B. The absolute roughness of a pipe de-creases with time

C. A pipe becomes smooth after using for long time

D. The absolute roughness increases with time
57. The increase in meta centric height_________________?
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A. increases comfort for passengers

B. decreases comfort for passengers</strong>

C. correct answer is?

D. decreases stability

E. increases stability
58. For hydro-dynamically smooth boundary, the friction coefficient for turbulent flow is_______________?
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A. a function of Reynolds number and relative roughness

B. constant

C. dependent on relative roughness only

D. dependent only on Reynolds number
59. Drag force is a function of________________?
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A. velocity of the body

B. projected area of the body

C. correct answer is ?

D. mass density of the fluid

60. The theoretical value of coefficient of contraction of a sharp edged orifice is_______________?
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A. 1

B. 0.85

C. 0.98

D. 0.611
61. The losses are more in_________________?
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A. critical flow

B. turbulent flow

C. transition flow

D. laminar flow

62. Select the incorrect statement?
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A. Coefficient of contraction is always less than one

B. Stream lines are parallel throughout the jet at vena contracta

C. The pressure intensity at vena contracta is atmospheric

D. Contraction is least at vena contracta

63. The correct relationship among displacement thickness d, momentum thickness m and energy thickness e is_________________?
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A. d > m > e

B. d > e > m

C. e > d > m

D. e > m > d

64. The discharge of a liquid of kinematic viscosity 4 cm2/sec through a 8 cm dia-meter pipe is 3200n cm7sec. The type of flow expected is__________________?
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A. not predictable from the given data

B. laminar flow

C. transition flow

D. turbulent flow

65. Centre of buoyancy always_________________?
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A. coincides with the centroid of the volume of fluid displaced

B. remains above the centre of gravity

C. coincides with the centre of gravity

D. remains below the centre of gravity

66. In case of an airfoil, the separation of flow occurs________________?
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A. any where between rear and front of body depending upon Reynolds number

B. at the extreme rear of body

C. at the extreme front of body

D. midway between rear and front of body

67. The horse power transmitted through a pipe is maximum when the ratio of loss of head due to friction and total head supplied is________________?
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A. 4-Jan

B. 3-Feb

C. 2-Jan

D. 1/3
68. Newtons law of viscosity relates________________?
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A. intensity of pressure and rate of angular deformation

B. shear stress and rate of angular deformation

C. viscosity and rate of angular deformation

D. shear stress, viscosity and temperature

69. The maximum thickness of boundary layer in a pipe of radius r is____________________?
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A. r/2

B. r

C. 0

D. 2r

70. The hydraulic grade line is_________________?
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A. always sloping downward in the direction of flow

B. never above the energy grade line

C. always above the centre line of pipe

D. all of the above

71. The point in the immersed body through which the resultant pressure of the liquid may be taken to act is known as__________________?
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A. center of gravity

B. metacentre

C. center of buoyancy

D. center of pressure
72. If a vessel containing liquid moves downward with a constant acceleration equal to g then_____________?
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A. there will be vacuum in the liquid

B. the pressure in the liquid mass is greater than hydrostatic pressure

C. the pressure throughout the liquid mass is atmospheric

D. none of the above

73. The major loss of energy in long pipes is due to_______________?
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A. sudden contraction

B. friction

C. gradual contraction or enlargement

D. sudden enlargement

74. A floating body is said to be in a state of stable equilibrium_________________?
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A. when the metacentre is below the centre of gravity

B. only when its centre of gravity is below its centre of buoyancy

C. when the metacentre is above the centre of gravity

D. when its metacentric height is zero

75. If a sphere of diameter 1 cm falls in castor oil of kinematic viscosity 10 stokes, with a terminal velocity of 1.5 cm/sec, the coefficient of drag on the sphere is________________?
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A. less than 1

B. 160

C. between 1 and 100

D. 200

76. Separation of flow occurs when_________________?
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A. the pressure intensity reaches a minimum

B. the cross-section of a channel is reduced

C. the boundary layer comes to rest

D. all of the above

77. In a Sutro weir, the discharge is proportional to________________?
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A. H

B. H3/2

C. H5/2

D. H1/2

78. For laminar flow in circular pipes, the Darcys friction factor f is equal to_________________?
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A. none of the above where R,, is Reynolds number

B. 64/ Re

C. 16/Re

D. 32/ Re

79. When the velocity distribution is uniform over the cross-section, the correction factor for momentum is__________________?
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A. 3-Apr

B. 1

C. 2

D. 0

80. Which of the following has highest coefficient of discharge ?
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A. venturimeter

B. sharp edged orifice

C. CipoUetti weir

D. Bordas mouthpiece running full

81. Two pipe systems are said to be equivalent when_________________?
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A. friction factor and length are same in two systems

B. length of pipe and discharge are same in two systems

C. head loss and discharge are same in two systems

D. length and diameter are same in two systems

82. The continuity equation pi V,A,= p2V2A2 is based on the following assumption regarding flow of fluid______________?
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A. uniform flow

B. incompressible flow

C. steady flow

D. frictionless flow

83. Coefficient of discharge for a totally submerged orifice as compared to that for an orifice discharging free is__________________?
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A. nearly half

B. slightly less

C. slightly more

D. equal

84. If the velocity is zero over half of the cross-sectional area and is uniform over the remaining half, then the momentum correction factor is_______________?
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A. 2

B. 3-Apr

C. 4

D. 1

85. Least possible value of correction factor for________________?
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A. kinetic energy is 1

B. momentum is zero

C. kinetic energy is zero

D. momentum is 1</strong>

86. Metacentric height for small values of angle of heel is the distance between the________________?
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A. free surface and centre of buoyancy

B. centre of gravity and metacentre

C. centre of gravity and centre of buoy-ancy

D. centre of buoyancy and metacentre

87. Which of the following is used to measure the discharge ?
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A. current meter

B. venturimeter

C. hotwire anemometer

D. pitot tube

88. Stream lines and path lines always coincide in case of__________________?
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A. steady flow

B. uniform flow

C. laminar flow

D. turbulent flow

89. Which of the following velocity potentials satisfies continuity equation ?
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A. x2y

B. cosx

C. x2-y2

D. x2 + y2

90. The wake_______________?
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A. is a region of high pressure intensity

B. always occurs before a separation point

C. none of the above

D. always occurs after a separation point
91. A fluid of kinematic viscosity 0.4 cm2/sec flows through a 8 cm diameter pipe. The maximum velocity for laminar flow will be__________________?
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A. 2 m/sec

B. 1.5 m/sec

C. 1 m/sec

D. less than 1 m/sec

92. For laminar flow in a pipe of circular cross-section, the Darcys friction factor f is________________?
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A. directly proportional to Reynolds number and independent of pipe wall roughness

B. inversely proportional to Reynolds number and directly proportional to pipe wall roughness

C. directly proportional to pipe wall roughness and independent of Reynolds number

D. inversely proportional to Reynolds number and indpendent of pipe wall roughness
93. Coefficient of velocity for Bordas mouth piece running full is________________?
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A. 0.855

B. 1

C. 0.707

D. 0.611

94. The total pressure on a plane surface inclined at an angle 9 with the horizontal is equal to_______________?
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A. PA

B. pA cos 9

C. pA sin 9

D. pA tan 9

95. When time of closure tc = L/v0 (where L is length of pipe and v0 is speed of pressure wavE., the portion of pipe length subjected to maximum head is__________________?
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A. L/2

B. L/4

C. L

D. L/3

96. The discharge through a V- notch varies as______________?
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A. H5/2

B. H54 where H is head

C. H1/2

D. H32

97. The velocity distribution for laminar flow through a circular tube__________________?
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A. varies linearly from zero at walls to maximum at centre

B. is constant over the cross-section

C. varies parabolically with maximum at the centre

D. none of the above

98. Ay between two stream lines represents________________?
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A. discharge

B. velocity

C. pressure

D. head