Question

What is the value of the included angle between two adjacent sides of the absolute best hydraulic trapezoidal open channel?

• A. \(60^\circ\)
• B. \(30^\circ\)
• C. \(120^\circ\)
• D. \(90^\circ\)

Hint:

For the most economical trapezoidal channel, \[ \boxed{ \theta=60^\circ \text{ (side with horizontal)} } \] Hence, the included interior angle is \[ \boxed{120^\circ.} \]

Answer 1

The Correct Option is C

Step 1: Recall the condition for the most economical trapezoidal channel. For an absolute best hydraulic trapezoidal section, - Half the top width equals the length of one sloping side. - The side makes an angle of \(60^\circ\) with the horizontal.

Step 2: Determine the included angle. Therefore, the included angle between the bed and the side is \[ 180^\circ-60^\circ=120^\circ. \] Hence, \[ \boxed{120^\circ} \] is the correct answer. Therefore, \[ \boxed{(C)} \] is the correct answer.