253. The best side slope for most economical trapezoidal section, is

A. 30?

B. 45?

C. 60?

D. None of these.

254. Pick up the correct statement from the followin For maximum velocity of flow, the depth of water in the circular channel must be 0.81 times the diameter of the channel

A. For maximum velocity, the hydraulic mean depth must be 0.3 times the diameter of circular channel

B. For maximum discharge the depth of flow must be 0.95 times the diameter of circular channel

C. All the above.

D.

255. For critical depth of flow of water in open channels, fe the specific energy must be :

A. minimum

B. maximum

C. average of maximum and minimum

D. None of these.

256. The velocity of flow at the critical depth (he) is called critical velocity (Vc) which is equal to

A. Vc = g x

B. V, = x h,

C. V = fg71T,

D. None of these.

257. For critical flow, the Froude number is :

A.1

B. less than 1.0

C. more than 1.0

D.2

258. The length of hydraulic jump is roughly

A. 2 to 3 times its height

B. 3 to 5 times its height

C. 5 to 7 times its height

D. None of these.

259. Orifice-meter is used to measure

A. pressure at the point

B. discharge

C. average speed

D. velocity.

Page **37** of **61**