# Hydraulics and Fluid Mechanics MCQ – Set 20

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## Q1. The divergent portion of a Venturimeter is made longer than convergent portion in order to

(A) Avoid the tendency of breaking away the stream of liquid
(B) To minimize frictional losses
(C) Both (A) and (B)
(D) None of these

## Q2. The buoyancy depends on

(A) Mass of liquid displaced
(B) Viscosity of the liquid
(C) Pressure of the liquid displaced
(D) Depth of immersion

Answer: (A) Mass of liquid displaced

## Q3. For very great pressures, viscosity of moss gases and liquids

(A) Remain same
(B) Increases
(C) Decreases
(D) Shows erratic behavior

## Q4. The discharge over a rectangular weir, considering the velocity of approach, is (whereH1 = H + Ha = Total height of water above the weir, H = Height of water over the crest of the weir, and Ha = Height of water due to velocity of approach)

(A) (2/3) Cd × L.√2g [H1 – Ha]
(B) (2/3) Cd × L. √2g [H13/2 – Ha3/2]
(C) (2/3) Cd × L.√2g [H12 – Ha2]
(D) (2/3) Cd × L. √2g [H15/2 – Ha5/2]

Answer: (B) (2/3) Cd × L. √2g [H13/2 – Ha3/2]

## Q5. In the case of steady flow of a fluid, the acceleration of any fluid particle is

(A) Constant
(B) Variable
(C) Zero
(D) Zero under limiting conditions

## Q6. The top of the weir over which the water flows is known as

(A) Sill or crest
(B) Nappe or vein
(C) Orifice
(D) None of these

## Q7. The velocity corresponding to Reynold number of 2000 is called

(A) Sub-sonic velocity
(B) Super-sonic velocity
(C) Lower critical velocity
(D) Higher critical velocity

(A) 10-2 m2/s
(B) 10-3 m2/s
(C) 10-4 m2/s
(D) 10-6 m2/s

## Q9. The error in discharge (dQ/Q) to the error in measurement of head (dH/H) over a rectangular notch is given by

(A) dQ/Q = (1/2) × (dH/H)
(B) dQ/Q = (3/4) × (dH/H)
(C) dQ/Q = (dH/H)
(D) dQ/Q = (3/2) × (dH/H)

Answer: (D) dQ/Q = (3/2) × (dH/H)

## Q1O. The centre of pressure for a vertically immersed surface lies at a distance equal to __ the centre of gravity.

(A) IG / Ax̅ bellow
(B) IG / Ax̅ above
(C) Ax̅ / IG bellow
(D) Ax̅ / IG above

Answer: (A) IG / Ax̅ bellow

## Q11. The conditions for the stable equilibrium of a floating body are

(A) The metacentre 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

Answer: (D) All the above are correct

(A) Equal to
(B) One-third
(C) Two-third
(D) Three-fourth

## Q13. The discharge through a channel of rectangular section will be maximum, if

(A) Its depth is twice the breadth
(B) Its breadth is twice the depth
(C) Its depth is thrice the breadth
(D) Its breadth is thrice the depth

## Q14. 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

Answer: (D) Difference of pressures between two points in a pipe

(A) Pressure
(B) Distance
(C) Density
(D) Flow

## Q16. The body will sink down 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

## Q17. The factional resistance of a pipe varies approximately with __ of the liquid.

(A) Pressure
(B) Velocity
(C) Square of velocity
(D) Cube of velocity

## Q18. According to Chezy’s formula, the discharge through an open channel is (where A = Area of flow, C = Chezy’s constant, m = Hydraulic mean depth, and i = Uniform slope in bed)

(A) A × √(m × i)
(B) C × √(m × i)
(C) AC × √(m × i)
(D) mi × √(A × C)

Answer: (C) AC × √(m × i)

## Q19. The centre of gravity of the volume of the liquid displaced is called

(A) Centre of pressure
(B) Centre of buoyancy
(C) Metacentre
(D) None of these