Fluid Mechanics Sheet 2

1) Question.

The point in the immersed body through which the resultant pressure of the liquid may be taken to act is known as -
Answer.
- 1
  
  centre of gravity
- 2
  
  centre of buoyancy
- 3
  
  centre of pressure
- 4
  
  metacentre
Answer: 3

Explanation:
2) Question.

A rectangular block 2 m long, 1 m wide and 1 m deep floats in water, the depth of immersion being 0.5 m. If water weighs $10 k N / m^{2}$ , then the weight of the block is -
Answer.
- 1
  
  5 kN
- 2
  
  10 kN
- 3
  
  15 kN
- 4
  
  20 kN
Answer: 2

Explanation:
3) Question.

One kilo-Pascal equivalent to -
Answer.
- 1
  
  $1 N / m m^{2}$
- 2
  
  $1000 N / m^{2}$
- 3
  
  $1000 N / m m^{2}$
- 4
  
  $1000 N / c m^{2}$
Answer: 2

Explanation:
4) Question.

A floating body is said to be in a state of stable equilibrium -
Answer.
- 1
  
  when its metacentric height is zero
- 2
  
  when the metacentre is above the centre of gravity
- 3
  
  when the metacentre is below the centre of gravity
- 4
  
  only when its centre of gravity is below its centre of buoyancy
Answer: 2

Explanation:
5) Question.

Metacentric height for small values of angle of heel is the distance between the -
Answer.
- 1
  
  centre of gravity and centre of buoyancy
- 2
  
  centre of gravity and metacentre
- 3
  
  centre of buoyancy and metacentre
- 4
  
  free surface and centre of buoyancy
Answer: 2

Explanation:
6) Question.

If the weight of a body immersed in a fluid exceeds the buoyant force, then the body will -
Answer.
- 1
  
  rise until its weight equals the buoyant force
- 2
  
  tend to move downward and it may finally sink
- 3
  
  float
- 4
  
  none of the above
Answer: 2

Explanation:
7) Question.

Centre of buoyancy always -
Answer.
- 1
  
  coincides with the centre of gravity
- 2
  
  coincides with the centroid of the volume of fluid displaced
- 3
  
  remains above the centre of gravity
- 4
  
  remains below the centre of gravity
Answer: 2

Explanation:
8) Question.

The position of centre of pressure on a plane surface immersed vertically in a static mass of fluid is -
Answer.
- 1
  
  at the centroid of the submerged area
- 2
  
  always above the centroid of the area
- 3
  
  always below the centroid of the area
- 4
  
  none of the above
Answer: 3

Explanation:
9) Question.

For a vertical semi-circular plate, sub-merged in a homogenous liquid with its diameter 'd' at the free surface, the depth of centre of pressure from the free surface is -
Answer.
- 1
  
  $\frac{3 πd}{32}$
- 2
  
  $\frac{3 d}{2 π}$
- 3
  
  $\frac{4 d}{3 π}$
- 4
  
  $\frac{3 πd}{16}$
Answer: 1

Explanation:
10) Question.

Pressure of 200 kPa is equivalent to a head of x metres of carbon tetra-chloride of relative density 1.59 where x is equal to -
Answer.
- 1
  
  11.62
- 2
  
  11.92
- 3
  
  12.82
- 4
  
  13.12
Answer: 3

Explanation:
11) Question.

The specific energy 'E' in a critical flow at depth $y_{c}$ occuring in a triangular channel is given by
Answer.
- 1
  
  $E = 1.25 y_{c}$
- 2
  
  $E = 1.5 y_{c}$
- 3
  
  $E = 1.75 y_{c}$
- 4
  
  $E = 2 y_{c}$
Answer: 1

Explanation:
12) Question.

Which of the following is a dimensionally homogeneous equation ?
Answer.
- 1
  
  $V = \frac{1}{n} R^{2 / 3} S^{1 / 2}$ (Manning's equation)
- 2
  
  $V = C \sqrt{R S}$ (Chezy's equation)
- 3
  
  $ρ = \frac{32 μ V L}{D^{2}}$ (Laminar flow in pipes)
- 4
  
  $N_{s} = \frac{N \sqrt{P}}{H^{3 / 4}}$ (specific speed of a turbine)
Answer: 3

Explanation:
13) Question.

The critical state of flow in a non-rectangular channel is expressed by
Answer.
- 1
  
  $y_{c} = {(\frac{q^{2}}{g})}^{1 / 3}$
- 2
  
  $\frac{Q^{2}}{g} = \frac{A^{3}}{T}$
- 3
  
  $\frac{Q^{3}}{g} = \frac{A^{2}}{T}$
- 4
  
  $\frac{Q^{2}}{g} = \frac{A}{T^{3}}$
Answer: 2

Explanation:
14) Question.

The kinetic energy correction factor is
Answer.
- 1
  
  applied to continuity equation
- 2
  
  expressed as $\frac{1}{A} \int_{A} {(\frac{v}{V})}^{2} d A$
- 3
  
  expressed as $\frac{1}{A} \int_{A} {(\frac{v}{V})}^{3} d A$
- 4
  
  expressed as $\frac{1}{A} \int_{A} (\frac{v}{V}) d A$
Answer: 3

Explanation:
15) Question.

The limit of the values of the coefficient of discharge of venturi meter is between
Answer.
- 1
  
  0.60 to 0.75
- 2
  
  0.76 to 0.80
- 3
  
  0.81 to 0.94
- 4
  
  0.95 to 0.99
Answer: 4

Explanation:
16) Question.

A surge tank is provided in a hydro-power scheme to
Answer.
- 1
  
  provide additional storage close to the penstock
- 2
  
  take care of change of slope, alignment or size of the water conductor
- 3
  
  reduce the pressures under transient conditions
- 4
  
  provide convenient overspills
Answer: 3

Explanation:
17) Question.

Which one of the following groups constitutes a set of parameters of identical dimensions ?
Answer.
- 1
  
  Velocity potential, stream function, velocity
- 2
  
  Power, torque, bending moment
- 3
  
  Relative roughness, friction factor, sub-layer thickness
- 4
  
  Rate of angular deformation, velocity gradient, speed in rpm
Answer: 1

Explanation:
18) Question.

If a sluice gate produces a change in the depth of water from 3.0 m to 0.6 m, then the force on the gate is about
Answer.
- 1
  
  9.5 kN/m
- 2
  
  19.0 kN/m
- 3
  
  38.0 kN/m
- 4
  
  76.0 kN/m
Answer: 3

Explanation:
19) Question.

In a normal shock wave in a one-dimensional flow, the
Answer.
- 1
  
  velocity, pressure and density increase
- 2
  
  pressure, density and temperature increase
- 3
  
  velocity, temperature and density increase
- 4
  
  pressure, density and momentum per unit time increase
Answer: 2

Explanation:
20) Question.

In a supersonic flow, a diverging passage results in
Answer.
- 1
  
  increase in the velocity and pressure
- 2
  
  increase in the velocity and density
- 3
  
  decrease in pressure and density
- 4
  
  decrease in velocity and pressure
Answer: 3

Explanation:

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