Hydraulics And Fluid Mechanics MCQ Questions & Answers

51

An ideal fluid is

A) one which obeys Newton’s law of viscosity B) frictionless and incompressible C) very viscous D) frictionless and compressible

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Answer & Solution

Answer: Option B

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52

In which of the following the friction drag is generally larger than pressure drag?

A) a circular disc or plate held normal to flow B) a sphere C) a cylinder D) an airfoil

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Answer & Solution

Answer: Option D

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53

A bucket of water is hanging from a spring balance. An iron piece is suspended into water without touching sides of bucket from another support. The spring balance reading will

A) increase B) decrease C) remain same D) increase/decrease depending on depth of immersion

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Answer & Solution

Answer: Option C

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54

Fluid is a substance which offers no resistance to change of

A) pressure B) flow C) shape D) volume

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Answer & Solution

Answer: Option C

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55

Choose the wrong statement.
Alcohol is used in manometer, because

A) its vapour pressure is low B) it provides suitable meniscus for the inclined tube C) its density is less D) it provides longer length for a given pressure difference

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Answer & Solution

Answer: Option A

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56

Alcohol is used in manometers because

A) it has low vapour pressure B) it is clearly visible C) it has low surface tension D) it can provide longer column due to low density

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Answer & Solution

Answer: Option D

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57

At the centre line of a pipe flowing under pressure where the velocity gradient is zero, the shear stress will be

A) minimum B) maximum C) negative value D) could be any value

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Answer & Solution

Answer: Option A

Solution:

In fluid mechanics, shear stress in a pipe flow is related to the velocity gradient (rate of change of velocity with respect to radial distance from the pipe wall).

In laminar flow through a circular pipe, the velocity is maximum at the center and decreases toward the pipe wall.

At the center line of the pipe, the velocity gradient is zero because the slope of the velocity profile flattens out at the peak.

Since shear stress is directly proportional to the velocity gradient, a zero velocity gradient results in zero shear stress.

Hence, the shear stress is minimum (actually zero) at the center line of the pipe.

Therefore, the correct answer is: minimum (Option A).

58

An open vessel of water is accelerated up an inclined plane. The free water surface will

A) be horizontal B) make an angle in direction of inclination of inclined plane C) make an angle in opposite direction to inclination of inclined plane D) any one of above is possible

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Answer & Solution

Answer: Option C

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59

The unit of kinematic viscosity is

A) gm/cm-sec² B) dyne-sec/cm² C) gm/cm²-sec D) cm²/sec

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Answer & Solution

Answer: Option D

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60

An open cubical tank of 2 m side is filled with water. If the tank is rotated with an acceleration such that half of the water spills out, then the acceleration is equal to

A) $$\frac{{\text{g}}}{3}$$ B) $$\frac{{\text{g}}}{2}$$ C) $$\frac{{2{\text{g}}}}{3}$$ D) $${\text{g}}$$

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Answer & Solution

Answer: Option D

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Hydraulics And Fluid Mechanics MCQ Questions & Answers | Civil Engineering