Difficulty: Medium
Correct Answer: All of the above
Explanation:
Introduction / Context:Chezy’s formula is widely used for uniform open-channel flow to relate mean velocity to hydraulic radius and slope. This problem checks competence in computing section properties and applying the velocity formula correctly.
Given Data / Assumptions:
Concept / Approach:
Hydraulic mean depth (hydraulic radius) R = A / P for open channels. Chezy’s velocity: V = C * √(R * S). Discharge: Q = A * V.
Step-by-Step Solution:
Area A = b * y = 6 * 3 = 18 m^2.Wetted perimeter P = b + 2 y = 6 + 6 = 12 m.Hydraulic radius R = A / P = 18 / 12 = 1.5 m.Mean velocity V = C * √(R * S) = 54.8 * √(1.5 * 1/2000).Compute inside root: 1.5/2000 = 0.00075; √(0.00075) ≈ 0.027386; V ≈ 54.8 * 0.027386 ≈ 1.5 m/s.Discharge Q = A * V = 18 * 1.5 = 27 m^3/s.Verification / Alternative check:
Dimensions: R in meters, S dimensionless; V in m/s; Q in m^3/s. Values are internally consistent and typical for a channel of this size and slope.
Why Other Options Are Wrong:
Since (a), (b), and (c) are all correct, any option omitting one of them is incomplete.
Common Pitfalls:
Using hydraulic depth A/b instead of hydraulic radius A/P; arithmetic slips with slope; forgetting the square root in Chezy’s relation.
Final Answer:
All of the above
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