# Fluid Mechanics Questions and Answers – Discharge over a Rectangular, Triangular, Trapezoidal & Stepped Notch

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This set of Fluid Mechanics Questions and Answers for Campus interviews focuses on “Discharge over a Rectangular Notch, Triangular Notch, Trapezoidal Notch and Stepped Notch”.

1. Find the discharge of water flowing over a rectangular notch of 1.5 m length when the constant head over the notch is 275 mm. Take Cd = .60
a) 400 lit/s
b) 465 lit/s
c) 385 lit/s
d) 575 lit/s

Explanation: Q = 2/3 * L * √2g * H1.5
= .67 * 1.5 * √19.62 * .2751.5
= .385 m3/min.

2. The head of water over a rectangular notch is 900 mm. The discharge is 300 litres/s. Find the length of the notch, when CD =.62
a) .192 m
b) .250 m
c) .205 m
d) .175 m

Explanation: L = 1.5 * Q / (Cd * √2g * H 1.5)
= 1.5 * .3 / (.62 * √19.62 * .91.5)
= .192 m.

3. Find the discharge of water flowing over a rectangular notch of 1.3 m length when the constant head over the notch is 255 mm. Take Cd = .62
a) 400 lit/s
b) 465 lit/s
c) 385 lit/s
d) 575 lit/s

Explanation: Q = 2/3 * L * √2g * H1.5
= .67 * 1.3 * √19.62 * .2551.5
= .385 m3/min.
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4. The head of water over a rectangular notch is 700 mm. The discharge is 200 litres/s. Find the length of the notch, when CD =.63
a) .125 m
b) .265 m
c) .250 m
d) .200 m

Explanation: L = 1.5 * Q / (Cd * √2g * H1.5)
= 1.5 * .2 / (.62 * √19.62 * .71.5)
= .125 m.

5. Find the discharge over triangular notch of angle 50° when the head over the V notch
a) .93 m3/min
b) 1.45 m3/min
c) .88 m3/min
d) .90 m3/min

Explanation: Q = 8/15 * √2g * H1.5 * tan(x)
Here, x is the angle.
= 8/15 * √19.62 * .221.5 * tan(50)
= .93 m3/min.

6. The expression for discharge for a right angled notch is more complex than rectangular notch.
a) True
b) False

Explanation: The expression for discharge for a right angled notch is easier than rectangular notch.

7. The results of which are more accurate; rectangular notch or triangular weir.
a) Rectangular notch
b) Triangular weir
c) Both are equally accurate
d) Rectangular weir

Explanation: The results of triangular notch are more accurate for low discharge.

8. What is main reading required in calculation for rectangular notch or weir.
a) H
b) x, x is angle
c) L
d) None of the mentioned

Explanation: H i.e height is main reading required in calculation for rectangular notch or weir.

9. We need to obligatorily have ventilation in triangular notch.
a) True
b) False

Explanation: We need not obligatorily have ventilation in triangular notch.

10. Rectangular notch may or may not have ventilation.
a) True
b) False

Explanation: Rectangular notch must have ventilation.

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