Fluid Mechanics MCQs Archives

121. Select the correct statement.

The discharge through a venturimeter depends upon ?p only and is independent of orientation of the meter

A venturimeter with a given gage difference discharges at a greater rate, when the flow is vertically downward through it, than when the flow is vertically upward

For a given pressure difference, the discharge of gas is greater through a venturimeter, when compressibility is taken into account, than when it is neglected

The overall pressure loss is the same in a given pipe line, whether a venturimeter or a nozzle with the same throat dia is used

✅ The correct answer is option A.

122. Function of air vessel provided in a reciprocating pump is to

Reduce discharge fluctuation

Reduce the danger of cavitation

Avoid the necessity of priming

Increase the pump efficiency

✅ The correct answer is option A.

123. Centre of pressure of a plane surface of arbitrary shape immersed vertically in a static mass of fluid

Lies above the centroid of the plane surface

Is independent of the specific weight of the fluid

Is different for different fluids

Is at the centroid of the plane surface

✅ The correct answer is option B.

124. A centrifugal pump has the following specifications: Power = 4 H.P.; Speed = 800 rpm Head = 8 metres Flow = 1000 litres/minutes. If its speed is halved, the new discharge will be __________ litres/minute.

500

200

1000

750

✅ The correct answer is option A.

125. Which of the following is not concerned with the fluid-particle interaction?

Drag co-efficient

Froude number

Galileo number

Weber number

✅ The correct answer is option D.

126. The hydraulic radius for flow in a rectangular duct of cross-sectional dimension H, W is

√(HW/π)

HW/2(H + W)²

HW/4(H + W)²

2HW/(H + W)²

✅ The correct answer is option B.

127. A gas (density = 1.5 kg/m³ , viscosity = 2x 10⁻⁵ kg/m.s) flowing through a packed bed (particle size = 0.5 cm, porosity = 0.5) at a superficial velocity of 2 m/s causes a pressure drop of 8400 Pa/m. The pressure drop for another gas, with density of 1.5kg/m³and viscosity of 3 x 10⁻⁵kg/m.s flowing at 3 m/s will be

8400 Pa/m

12600 Pa/m

18900 Pa/m

16800 Pa/m

✅ The correct answer is option B.

128. The location of centre of pressure, which defines the point of application of the total pressure force on the surface, can be calculated by applying the principle of moments according to which “sum of the moment of the resultant force about an axis is equal to the sum of the components about the same axis”. The centre of pressure of a rectangular surface (of width ‘w’) immersed vertically in a static mass of fluid is at a depth of(where, y = depth of the liquid)

1/3y

2y/3

1/4y

3y/4

✅ The correct answer is option B.

129. A 0.5 m high bed made up of a 1 mm dia glass sphere (density 2500 kg/m³ ) is to be fluidised by water (density 1000 kg/m³ ). If at the point of incipient fluidisation, the bed voidage is 40%, the pressure drop across the bed is

4.4 KPa

2.94 KPa

3.7 KPa

None of these

✅ The correct answer is option A.

130. The terminal velocity of a particle moving through a fluid varies as dpn. What is the value of n’ for Newton’s law regime?

0.5

1.5

✅ The correct answer is option A.