246. The flow in open channel is said to be subcritical if the Froude number is

A. less than 1.0

B. equal to 1.0

C. greater than 1.0

D. none.

247. The flow in open channel is said to be critical if the Froude number is :

A. less than 1.0

B.,equal to 1.0

C. greater than 1.0

D. None of these.

248. A rectangular channel 6 m wide and 3 m deep and having a bed slope as 1 in 2000 is running full. If Chezy's constant C = 54.8, pick up the correct specification of the channel from the following :

A. hydraulic mean depth = 1.5 m

B. Velocity of flow = 1.5 m/sec

C. Rate of flow = 27 m3/sec

D. All the above.

249. For a most economical rectangular channel, the width of the channel must be

A. equal to depth of flow

B. twice the depth of flow

C. half the depth of flow

D. None of these.

250. For a most economical rectangular channel, the hydraulic mean depth, is equal to

A. the depth of flow

B. half the depth of flow

C. one-third depth of flow

D. None of these.

251. For a most economical trapezoidal open channel, the half of the top width must be equal to

A. the bed width

B. one sloping side

C. the depth of flow

D. None of these.

252. For the most economical trapezoidal open channel,

A. half of the top width must be equal to one of the sloping sides

B. the hydraulic mean depth must be equal to half the depth of flow

C. the semicircle drawn with top width as diameter must touch the three sides of the channel

D. All of these.

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