Category: FLUID MECHANICS Questions

100 TOP FLUID MECHANICS Multiple Choice Questions and Answers<—-CLICK HERE

86. Select the correct statement.
a) The absolute roughness of a pipe de-creases with time.
b) A pipe becomes smooth after using for long time.
c) The friction factor decreases with time.
d) The absolute roughness increases with time.
Ans: d
87. 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
a) 1 m
b) 10m
c) 100m
d) none of the above
Ans: c
88. The speed of a pressure wave through a pipe depends upon
a) the length of pipe
b) the viscosity of fluid
c) the bulk modulus for the fluid
d) the original head
Ans: c
89. 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
a) L/4
b) L/3
c) L/2
d) L
Ans: a
90. If the elevation of hydraulic grade line at the junction of three pipes is above the elevation of reservoirs B and C and below reservoir A, then the direction of flow will be
a) from reservoir A to reservoirs B and C
b) from reservoir B to reservoirs C and A
c) from reservoir C to reservoirs A and B
d) unpredictable
Ans: c

a) 3.75 m
b) 4.0 m
c) 4.2m
d) 4.5m
Ans: c

a) velocity at stagnation point
b) stagnation pressure
c) static pressure
d) dynamic pressure
Ans: b

a) The pressure intensity at vena contracta is atmospheric.
b) Contraction is least at vena contracta.
c) Stream lines are parallel throughout the jet at vena contracta.
d) Coefficient of contraction is always less than one.
Ans: c

100 TOP FLUID MECHANICS Multiple Choice Questions and Answers pdf<—– CLICK HERE

91. The length of a pipe is 1 km and its diameter is 20 cm. If the diameter of an equivalent pipe is 40 cm, then its length is
a) 32 km
b) 20 km
c) 8 km
d) 4 km
Ans: a
92. Two pipes of same length and diameters d and 2d respectively are connected in series. The diameter of an equivalent pipe of same length is
a) less than d
b) between d and 1.5 d
c) between 1.5 d and 2d
d) greater than 2d
Ans: a
93. The horse power transmitted through a pipe is maximum when the ratio of loss of head due to friction and total head supplied is
a) 1/3
b) 1/4
c) 1/2
d) 2/3
Ans: a
94. The boundary layer thickness at a distance of l m from the leading edge of a flat plate, kept at zero angle of incidence to the flow direction, is O.l cm. The velocity outside the boundary layer is 25 ml sec.
The boundary layer thickness at a distance of 4 m is
a) 0.40 cm
b) 0.20 cm
c) 0.10 cm
d) 0.05 cm
Assume that boundary layer is entirely laminar.
Ans: b
95. Drag force is a function of
i) projected area of the body
ii) mass density of the fluid
iii) velocity of the body
The correct answer is
a) (i) and (ii)
b) (i) and (iii)
c) (ii) and (iii)
d) (i), (ii) and (iii)
Ans: d

a) coincides with the centre of gravity
b) coincides with the centroid of the volume of fluid displaced
c) remains above the centre of gravity
d) remains below the centre of gravity
Ans: b