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# MCQs on Discharge over a Rectangular, Triangular, Trapezoidal & Stepped Notch

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

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c

Explanation: Q = 2/3 * L * √2g * H1.5

= .67 * 1.5 * √19.62 * .2751.5

= .385 m3/min.

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

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a

Explanation: L = 1.5 * Q / (Cd * √2g * H 1.5)

= 1.5 * .3 / (.62 * √19.62 * .91.5)

= .192 m.

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

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a

Explanation: Q = 2/3 * L * √2g * H1.5

= .67 * 1.3 * √19.62 * .2551.5

= .385 m3/min.

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

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a

Explanation: L = 1.5 * Q / (Cd * √2g * H1.5)

= 1.5 * .2 / (.62 * √19.62 * .71.5)

= .125 m.

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

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a

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.

The expression for discharge for a right angled notch is more complex than rectangular notch.

a) True

b) False

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b

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

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

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b

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

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

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a

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

We need to obligatorily have ventilation in triangular notch.

a) True

b) False

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b

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

Rectangular notch may or may not have ventilation.

a) True

b) False

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b

Explanation: Rectangular notch must have ventilation.