Fluid Mechanics MCQ Objective Question and Answers Part 2

Fluid Mechanics Multiple choice Objective Question useful for technical Aptitude test.

Fluid Mechanics MCQ : Part 1 | Part 2 | Part 3 | Part 4 | Part 5

51. 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
(e) h/wh.
Ans: b

52. 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 in-crease in temperature
(d) Viscosity of liquids is appreciably affected by change in pressure
(e) Viscosity is expressed as poise, stoke, or saybolt seconds.
Ans: d

53. The units of kinematic viscosity are

(a) metres2 per sec
(b) kg sec/metre
(c) newton-sec per metre
(d) newton-sec per metre
(e) none of the above.
Ans: a

54. The ratio of absolute viscosity to mass density is known as

(a) specific viscosity

(b) viscosity index
(c) kinematic viscosity
(d) coefficient of viscosity
(e) coefficient of compressibility.
Ans: c

55. Kinematic viscosity is equal to

(a) dynamic viscosity/density
(b) dynamicviscosity x density
(c) density/dynamic viscosity
(d) 1/dynamicviscosity x density
(e) same as dynamic viscosity.
Ans: a

56. Which of the following is the unit of kinematic viscosity

(a) pascal
(b) poise
(c) stoke
(d) faraday
(e) none of the above.
Ans: c

57. 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
(e) takes place in one dimension.

Ans: d

58. 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
(e) is provides suitable meniscus.
Ans: d

59. 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) 2.5kN/m2
(e) 12.5 kN/m2.
Ans: b

60. Specific weight of sea water is more that of pure water because it contains

(a) dissolved air
(b) dissolved salt
(c) suspended matter
(d) all of the above
(e) heavy water.
Ans: d

61. If 850 kg liquid occupies volume of one cubic meter, men 0.85 represents its

(a) specific weight
(b) specific mass
(c) specific gravity
(d) specific density
(e) none of the above.
Ans: c

62. Free surface of a liquid tends to contract to the smallest possible area due to force of

(a) surface tension
(b) viscosity
(c) friction
(d) cohesion
(e) adhesion.
Ans: a

63. 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
(e) unpredictable.
Ans: c

64. Falling drops of water become spheres due to the property of

(a) adhesion

(b) cohesion
(c) surface tension
(d) viscosity
(e) compressibility.
Ans: c

65. A liquid would wet the solid, if adhesion forces as compared to cohesion forces are

(a) less
(b) more
(c) equal
(d) less at low temperature and more at high temperature
(e) there is no such criterion.
Ans: b

66. 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
(e) none of the above.
Ans: c

67. 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
(e) none of the above.
Ans: b

68. 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
(e) 4000 kg.
Ans: d

69. The resultant upward pressure of a fluid on a floating body is equal to the weight of the fluid displaced by the body. This definition is according to

(a) Buoyancy
(b) Equilibrium of a floating body
(c) Archimedes’ principle
(d) Bernoulli’s theorem
(e) Metacentric principle.
Ans: c

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

(a) upthrust
(b) buoyancy
(c) center of pressure
(d) all the above are correct
(e) none of above is correct.
Ans: b

71. The conditions for the stable equilibrium of a floating body are

(a) the meta-center should lie above the center of gravity

(b) the center of buoyancy and the center of gravity must lie on the same vertical line
(c) a righting couple should be formed
(d) all the above are correct
(e) none of the above is correct.
Ans: d

72. Poise is the unit of

(a) surface tension
(b) capillarity
(c) viscosity

(d) shear stress in fluids
(e) buoyancy.
Ans: c

73. Metacentric height is given as the distance between

(a) the center of gravity of the body and the meta center
(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
(e) none of the above.
Ans: a

74. The buoyancy depends on

(a) mass of liquid displaced
(b) viscosity of the liquid
(c) pressure of the liquid displaced
(d) depth of immersion
(e) none of the above.
Ans: a

75. The center of gravity of the volume of the liquid displaced by an immersed body is called

(a) meta-center
(b) center of pressure
(c) center of buoyancy
(d) center of gravity
(e) none of the above.
Ans: c

76. 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
(e) none of the above.
Ans: c

77. 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
(e) none of die above.
Ans: c

78. 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
(e) none of die above.
Ans: b

79. Rain drops are spherical because of

(a) viscosity
(b) air resistance
(c) surface tension forces
(d) atmospheric pressure
(e) none of the above.
Ans: c

80. 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
(e) viscosity.
Ans: b

81. The capillary rise at 20°C in a clean glass tube of 1 mm bore containing water is approximately

(a) 1 mm
(b) 5 mm
(c) 10 mm
(d) 20 mm
(e) 30 mm.
Ans: e

82. The difference of pressure between the inside and outside of a liquid drop is

(a)p = Txr
(b)p = T/r
(c) p = T/2r
(d)p = 2T/r
(e) none of the above.
Ans: d

83. 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
(e) none of the above.
Ans: c

84. 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
(e) none of the above.
Ans: b

85. To avoid an interruption in the flow of a syphon, an air vessel is provided

(a) at the inlet
(b) at the outlet
(c) at the summit
(d) ay nay point between inlet and outlet
(e) none of the above.
Ans: c

86. 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
(e) none of the above.
Ans: a

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

(a) surface tension
(b) co-efficient of viscosity
(c) viscosity
(d) osmosis
(e) cohesion.
Ans: c

88. The process of diffusion of one liquid into the other through a semi-permeable membrane is called

(a) viscosity
(b) osmosis
(c) surface tension
(d) cohesion
(e) diffusivity.
Ans: b

89. 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

Ans: c

90. The continuity equation is connected with

(a) viscous/unviscous fluids
(b) compressibility of fluids
(c) conservation of mass
(d) steady/unsteady flow
(e) open channel/pipe flow.
Ans: c

91. The rise or depression of liquid in a tube due to surface tension increase in size of tube will

(a) increase
(b) remain unaffected
(c) may increase or decrease depending on the characteristics of liquid
(d) decrease
(e) unpredictable.
Ans: d

92. 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
(e) Chezy’s equation.
Ans: c

93. 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
(e) none of the above.
Ans: d

94. Newton’s law of viscosity is a relationship between

(a) shear stress anctthejiate of angular distortion
(b) shear stress and viscosity
(c) shear stress, velocity and viscosity
(d) pressure, velocity and viscosity
(e) shear stress, pressure and rate of angular distortion.
Ans: a

95. The atmospheric pressure with rise in altitude decreases

(a) linearly
(b) first slowly and then steeply
(c) first steeply and then gradually
(d) unpredictable
(e) none of the above.
Ans: b

96. Pressure of the order of 10″‘ torr can be measured by

(a) Bourdon tube
(b) Pirani Gauge
(c) micro-manometer
(d) ionisastion gauge
(e) McLeod gauge.
Ans: d

97. Operation of McLeod gauge used for low pressure measurement is based on the principle of

(a) gas law
(b) Boyle’s law
(c) Charle’s law
(d) Pascal’s law
(e) McLeod’s law.
Ans: b

98. An odd shaped body weighing 7.5 kg and occupying 0.01 m3 volume will be completely submerged in a fluid having specific gravity of

(a) 1
(b) 1.2
(c) 0.8
(d) 0.75
(e) 1.25.
Ans: d

99. In an isothermal atmosphere, the pressure

(a) decreases linearly with elevation
(b) remains constant
(c) varies in the same way as the density
(d) increases exponentially with elevation

(e) unpredictable.
Ans: c

100. 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)
(e) it moves easily.
Ans: d