Bernoulli and Flow Measurement
JKSSB Junior Engineer (Civil) · Fluid Mechanics and Hydraulics · 24 practice questions with answers and explanations: 12 Easy, 9 Medium, 3 Hard.
Sample questions
Sample Easy question 1
A broad-crested weir works with a crest that is:
- Circular
- Sharp and thin
- Triangular
- Wide in the direction of flow so the flow becomes parallel at the crest
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Answer: D. The flow passes through the critical depth over the crest.
Sample Easy question 2
The coefficient of contraction of a sharp-edged orifice is the ratio of:
- The head to the area
- The area of the jet at the vena contracta to the area of the orifice
- The actual velocity to the theoretical velocity
- The actual discharge to the theoretical discharge
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Answer: B. Its value is about 0.62.
Sample Easy question 3
The momentum equation is used to find:
- The viscosity
- The force exerted by a flowing fluid on a bend, nozzle or plate
- The pressure at rest
- The compressibility
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Answer: B. F = ρ Q (v₂ − v₁) for a change in velocity.
Sample Medium question 4
The discharge through a small orifice of area 0.005 m² with a coefficient of discharge of 0.6 under a head of 4 m is about:
- 0.00266 m³/s
- 0.0266 m³/s
- 0.266 m³/s
- 0.0443 m³/s
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Answer: B. Q = C_d × a × √(2gh) = 0.6 × 0.005 × √(2 × 9.81 × 4) = 0.0266 m³/s.
Sample Medium question 5
The discharge over a 90° V-notch with C_d = 0.6 under a head of 0.25 m is about:
- 0.12 m³/s
- 0.0044 m³/s
- 0.44 m³/s
- 0.044 m³/s
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Answer: D. Q = (8 ÷ 15) × C_d × tan 45° × √(2g) × H^(5/2) = 0.0443 m³/s.
Sample Medium question 6
A Pitot tube in flowing water shows a stagnation head of 0.2 m above the static head. The velocity of flow is about:
- 0.99 m/s
- 3.96 m/s
- 9.81 m/s
- 1.98 m/s
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Answer: D. v = √(2gh) = √(2 × 9.81 × 0.2) = 1.98 m/s.
Sample Hard question 7
A venturimeter has an inlet area of 0.03 m², a throat area of 0.015 m² and a head difference of 0.4 m of water, with C_d = 0.98. The discharge is about:
- 0.067 m³/s
- 0.095 m³/s
- 0.024 m³/s
- 0.048 m³/s
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Answer: D. Q = C_d A₁A₂ √(2gh) ÷ √(A₁² − A₂²) = 0.0476 m³/s.
Sample Hard question 8
A tank of area 4 m² with a head of 4 m above a small orifice of area 0.005 m² (C_d = 0.6) empties in about:
- 1,204 s
- 602 s
- 20.1 s
- 2,408 s
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Answer: A. t = 2A (√H₁ − √H₂) ÷ (C_d a √(2g)) = 2 × 4 × 2 ÷ (0.6 × 0.005 × 4.429) = 1,204 s.
Sample Hard question 9
A rectangular weir 3.0 m long with 2 end contractions under a head of 0.4 m has an effective length (Francis, L − 0.1 n H) of:
- 2.8 m
- 3 m
- 2.92 m
- 2.2 m
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Answer: C. L' = 3.0 − 0.1 × 2 × 0.4 = 2.92 m.