Top 1000+ Solved Fluid Mechanics (FM) MCQ Questions Answer
Q. Two pipe systems are said to be equivalent when
a. head loss and discharge are same in two systems
b. length of pipe and discharge are same in two systems
c. friction factor and length are same in two systems
d. length and diameter are same in two systems
Q. In series-pipe problems
a. the head loss is same through each pipe
b. the discharge is same through each pipe
c. a trial solution is not necessary
d. the discharge through each pipe is added to obtain total discharge
Q. 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.
Q. 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
Q. 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
Q. 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
Q. The length of a pipe is 1 km and its diameter is 20 cm. If the diameter ofan equivalent pipe is 40 cm, then its length is
a. 32 km
b. 20 km
c. 8 km
d. 4 km
Q. 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
Q. 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 (Assume that boundary layer is entirely laminar.)
a. 0.40 cm
b. 0.20 cm
c. 0.10 cm
d. 0.05 cm
Q. 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)
Q. The correct relationship among displacement thickness d, momentumthickness m and energy thickness e is
a. d > m > e
b. d > e > m
c. e > m > d
d. e > d > m
Q. For laminar flow in circular pipes, the Darcy’s friction factor f is equal to
a. 16/Re
b. 32/ Re
c. 64/ Re
d. none of the above where R,, is Reynolds number.
Q. Surge wave in a rectangular channel is an example ofi) steady flow ii) unsteady flow iii) uniform flow iv) non-uniform flow The correct answer is
a. (i) and (iii)
b. (ii) and (iii)
c. (i) and (:v)
d. (ii) and (iv)