Most Economic Rectangular Section - Fluid Mechanics Questions and Answers

This set of Fluid Mechanics Multiple Choice Questions & Answers (MCQs) focuses on “Most Economic Rectangular Section”.

1. For a channel to be economic which of the following parameters should be minimum.
a) Wetted perimeter
b) Wetted area
c) Section factor
d) Hydraulic depth
View Answer

Answer: a
Explanation: If the wetted perimeter is minimum, amount of materials required for construction of the channel is less and hence the channel is more economical.

2. A rectangular channel section has depth y and width B, calculate the most economical area of the channel.
a) 2y²
b) y²
c) By
d) B²
View Answer

Answer: a
Explanation:

Find economical area of channel for rectangular channel section has depth y & width B

3. The depth and widths of a rectangular channel section are y and B respectively, determine the economical perimeter of the section.
a) y
b) 2y
c) 3y
d) 4y
View Answer

Answer: d
Explanation:

Perimeter of section is 4y if depth & widths of rectangular channel section are y & B

4. Calculate the hydraulic radius for the most economical rectangular section having depth y and width B.
a) y/2
b) y
c) 2y
d) 3y
View Answer

Answer: a
Explanation:

Find hydraulic radius for economical rectangular section having depth y & width B

5. Calculate the maximum discharge through a rectangular channel having depth 3m, bed slope of 1 in 1000.
a) 33.85m³/s
b) 34.85m³/s
c) 35.85m³/s
d) 36.85m³/s
View Answer

Answer: b
Explanation:

Find maximum discharge through rectangular channel having depth 3m, bed slope of 1 in 1000

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6. Calculate the maximum discharge through a rectangular channel having width of 5m, bed slope of 1 in 500 and manning’s co efficient is 0.020.
a) 33.43m³⁄s
b) 32.43m³⁄s
c) 31.43m³⁄s
d) 30.43m³⁄s
View Answer

Answer: b
Explanation:

Maximum discharge through rectangular channel having width of 5m is 30.43m3/s

7. The maximum discharge through a rectangular channel is 7.15m³⁄s, determine the depth of the channel where S₀ = 1/2000 and C=40.
a) 4m
b) 3m
c) 2m
d) 1m
View Answer

Answer: c
Explanation:

Find the depth of the channel where S0 = 1/2000 & C=40

8. The base width of a most economical rectangular channel is 8m, calculate the hydraulic radius of the channel,
a) 5m
b) 4m
c) 3m
d) 2m
View Answer

Answer: d
Explanation: B = 2y; y = 4m
R = y/2 = 2m.

9. Calculate the section factor for the most economical rectangular section having depth of 4m.
a) 32
b) 64
c) 128
d) 256
View Answer

Answer: b
Explanation: Z = A√D = 2y² √y = 2y^5/2
Z = 64.

10. The ratio between maximum discharge and top width of a rectangular channel is 91:50, calculate the depth of the channel if the bed slope is 1 in 3000 and C = 50.
a) 2m
b) 3m
c) 4m
d) 5m
View Answer

Answer: a
Explanation:

Find the depth of the channel if the bed slope is 1 in 3000 & C = 50

11. The ratio between normal discharge and maximum discharge through a rectangular channel is 32:6, calculate the depth of the channel if the width of the channel is 4m and bed slope, chezy’s constant remains same.
a) 1m
b) 2m
c) 3m
d) 4m
View Answer

Answer: a
Explanation:

Find the depth of the channel if the width of the channel is 4m & bed slope

12. The hydraulic radius of an economical rectangular section is 4m, calculate the discharge through the channel if the bed slope of the channel is 1 in 1000 and manning’s co efficient is 0.015.
a) 680m³⁄s
b) 690m³⁄s
c) 700m³⁄s
d) 710 m³⁄s
View Answer

Answer: a
Explanation: