Hydraulics And Fluid Mechanics MCQ Questions & Answers

41

True one-dimensional flow occurs when

A) the direction and magnitude of the veiocity at all points are identical B) the velocity of successive fluid par-ticles, at any point, is the same at suc-cessive periods of time C) the magnitude and direction of the velocity do not change from point to point in the fluid D) the fluid particles move in plane or parallel planes and the streamline pat-terns are identical in each plane

Discuss

Answer & Solution

Answer: Option A

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42

Non uniform flow occurs when

A) the direction and magnitude of the velocity at all points are identical B) the velocity of successive fluid par-ticles, at any point, is the same at suc-cessive periods of time C) the fluid particles move in plane or parallel planes and the streamline pat-terns are identical in each plane D) velocity, depth, pressure, etc. change from point to point in the fluid flow.

Discuss

Answer & Solution

Answer: Option D

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43

In a Sutro weir, the discharge is proportional to (where H is head)

A) $${{\text{H}}^{\frac{1}{2}}}$$ B) $${{\text{H}}^{\frac{3}{2}}}$$ C) $${{\text{H}}^{\frac{5}{2}}}$$ D) $${\text{H}}$$

Discuss

Answer & Solution

Answer: Option D

No explanation is given for this question. Let's Discuss on Board

44

If 850 kg liquid occupies volume of one cubic meter, men 0.85 represents its

A) specific weight B) specific mass C) specific gravity D) specific density

Discuss

Answer & Solution

Answer: Option C

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45

Free surface of a liquid tends to contract to the smallest possible area due to force of

A) surface tension B) viscosity C) friction D) cohesion

Discuss

Answer & Solution

Answer: Option A

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46

A perfect gas

A) has constant viscosity B) is incompressible C) is of theoretical interest D) none of the above.

Discuss

Answer & Solution

Answer: Option C

Solution:

A perfect gas is an idealized concept used in fluid mechanics and thermodynamics to simplify analysis.

It strictly follows the ideal gas laws and assumes conditions such as no intermolecular forces and perfect elasticity of molecules.

In reality, no gas satisfies all these assumptions, so a perfect gas is not incompressible and does not have constant viscosity under all conditions.

Therefore, a perfect gas is mainly of theoretical interest, making option C the correct answer.

47

For a floating body to be in stable equilibrium, its metacentre should be

A) below the center of buoyancy B) above the center of buoyancy C) between e.g. and center of pressure D) above the center of gravity.

Discuss

Answer & Solution

Answer: Option D

No explanation is given for this question. Let's Discuss on Board

48

The resultant of all normal pressures acts

A) at e.g. of body B) at center of pressure C) vertically upwards D) at metacentre

Discuss

Answer & Solution

Answer: Option B

Solution:

The resultant of all normal pressures in a fluid acts at the center of pressure. The center of pressure is the point where the total force due to fluid pressure can be considered to act on a submerged surface. It is essential in the analysis of fluid forces on submerged surfaces.

Therefore, the correct answer is Option B: at center of pressure.

49

Pressure of the order of 10''' torr can be measured by

A) Bourdon tube B) Pirani Gauge C) micro-manometer D) ionisastion gauge

Discuss

Answer & Solution

Answer: Option D

Solution:

Pressures of the order of 10⁻⁷ torr (very high vacuum) are extremely low and cannot be measured by ordinary pressure-measuring devices.

A Bourdon tube is used for measuring relatively high pressures and is unsuitable for vacuum measurements.

A micro-manometer is used for small pressure differences but not for very high vacuum ranges.

A Pirani gauge can measure low pressures only up to about 10⁻³ torr.

An ionisation gauge operates on the principle of ionizing gas molecules and is specifically designed to measure very low pressures (high vacuum) of the order of 10⁻⁷ torr and below.

Hence, the correct answer is ionisation gauge.

50

Flow of water in a pipe about 3 meters in diameter can be measured by

A) orifice plate B) venturi C) rotameter D) pitot tube

Discuss

Answer & Solution

Answer: Option D

Solution:

Flow measurement in large diameter pipes, such as a 3-meter diameter water pipe, requires devices that can handle high flow rates and provide accurate readings with minimal energy loss.

An orifice plate causes significant head loss and is more suitable for smaller pipes.

A rotameter is typically used for low flow rates and smaller pipe diameters in vertical applications.

A pitot tube can measure velocity at a point but is not practical for measuring total flow in such a large pipe.

The venturi meter is specifically designed to measure flow in large pipes. It operates on the principle of pressure differential and causes minimal energy loss.

Therefore, for a pipe about 3 meters in diameter, the most suitable device is the venturi meter.

Correct answer is Option B: venturi

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