Fluid Mechanics MCQ Set 10
FLUID MECHANICS MCQ SET 10
Q1. The device used to measure flow rate in an open channel is called:
A) Venturi meter
B) Orifice meter
C) Notch or Weir
D) Pitot tube
Show Answer
Answer: C) Notch or Weir
Explanation: Notches and weirs are standard devices to measure discharge in open channel flows.
Q2. A rectangular weir measures:
A) Pressure
B) Flow rate
C) Temperature
D) Viscosity
Show Answer
Answer: B) Flow rate
Explanation: Rectangular weirs are used in laboratory and field conditions to calculate discharge over a barrier.
Q3. A cylindrical vessel of radius R and height h is completely filled with water. The total pressure on the base is:
A) ρgh
B) ρgπR²h
C) ρgh²
D) ρgR²
Show Answer
Answer: B) ρgπR²h
Explanation: Total pressure = pressure × area = (ρgh) × (πR²).
Q4. A flow with constant velocity magnitude but changing direction is called:
A) Uniform flow
B) Steady flow
C) Rotational flow
D) Irrotational flow
Show Answer
Answer: C) Rotational flow
Explanation: When direction changes, vorticity exists — making the flow rotational even if speed is constant.
Q5. The continuity equation in one-dimensional steady flow is:
A) A₁V₁ = A₂V₂
B) A₁/V₁ = A₂/V₂
C) A₁V₁² = A₂V₂²
D) None
Show Answer
Answer: A) A₁V₁ = A₂V₂
Explanation: Conservation of mass ensures discharge (A×V) remains constant in steady flow.
Q6. For compressible flow, the continuity equation includes:
A) Temperature
B) Density variation
C) Pressure ratio
D) Gravity
Show Answer
Answer: B) Density variation
Explanation: In compressible flow, density (ρ) varies, so the equation becomes ρ₁A₁V₁ = ρ₂A₂V₂.
Q7. The head loss due to sudden enlargement of pipe is:
A) (V₁ – V₂)² / 2g
B) (V₂ – V₁)² / 2g
C) (V₁ + V₂)² / 2g
D) None
Show Answer
Answer: A) (V₁ – V₂)² / 2g
Explanation: Energy loss occurs due to eddies and turbulence when pipe cross-section increases suddenly.
Q8. The pressure energy per unit weight of fluid is:
A) p/ρ
B) p/γ
C) pV
D) p×h
Show Answer
Answer: B) p/γ
Explanation: Pressure energy per unit weight = (pressure) / (specific weight) = p/γ.
Q9. The force exerted by a fluid jet on a stationary flat plate normal to jet is:
A) ρaV²
B) ρaV
C) ρaV²/2
D) ρaV³
Show Answer
Answer: A) ρaV²
Explanation: Force = rate of change of momentum = mass flow × velocity = ρAV².
Q10. The phenomenon of water hammer occurs due to:
A) Sudden closure of valve
B) Gradual valve opening
C) Air bubbles in flow
D) Cavitation
Show Answer
Answer: A) Sudden closure of valve
Explanation: When a valve closes suddenly, moving water stops abruptly, creating a high-pressure shock wave called water hammer.