Flow Through Pipes MCQ with answer and solution

Concept

Water hammer is a pressure surge caused by suddenly stopping the flow in a pipe, for example by quick valve closure.

Formula

Pressure rise for sudden closure: p = ρ × C × V, where C = √(K/ρ)

Step-by-step solution

1. Water hammer happens when moving water is stopped suddenly, for example when a valve is closed quickly. 2. Water hammer arrestors absorb the pressure surge, so (A) is a remedy. 3. Draining and refilling pipes recreates air chambers that act as a cushion, so (B) is a remedy. 4. Tightening mounting straps stops pipe movement and banging, so (D) is a remedy. 5. Closing a valve suddenly causes water hammer and does not prevent it, so (C) is NOT a remedial measure.

Explanation

Sudden valve closure stops the water quickly and creates a high pressure wave. This is the cause of water hammer, not its cure. All the other options either absorb the surge or reduce pipe movement.

Why the other options are wrong

(A) Arrestors absorb the shock. (B) Air chambers cushion the surge. (D) Tight straps reduce pipe vibration and noise.

Shortcut

Any option about sudden valve closure is a cause of water hammer, not a remedy.

Common mistake

Thinking that closing a valve controls the flow safely. Only slow closure is safe, while sudden closure causes water hammer.