61. The base width of an elementary profile of gravity dam of height H is b. The specific gravity of the material of the dam is G and uplift pressure coefficient is K. The correct relationship for no tension at the heel is given by

1. 1. b	=	1
      H		√G - K

   
   
   

   2. 	b	= √G - K
      	H

   
   
   

   3. b	=	1
      H		G - K

   
   
   

   4. b	=	1
      H		K√G - K

   
   
   

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   NA

   Correct Option: A

   NA

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62. A horizontal jet of water with its cross-sectional area of 0.0028 m² hits a fixed vertical plate with a velocity of 5 m/s. After impact the jet splits symmetrically in a plane parallel to the plane of the plate. The force of impact (in N) of the jet on the plate is

1. 1. 90

   
   
   

   2. 80

   
   
   

   3. 70

   
   
   

   4. 60

   
   
   

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   Force on plate = (r_a av)v
   = ra .aV²
   = 1000 × 0.0028 × 5²
   = 70 N

   Correct Option: C

   Force on plate = (r_a av)v
   = ra .aV²
   = 1000 × 0.0028 × 5²
   = 70 N

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63. If the pump head is 75 m, discharge is 0.464 m³ /s and the motor speed is 1440 rpm at rated condition, the specific-speed of the pump is about

1. 1. 4

   
   
   

   2. 26

   
   
   

   3. 38

   
   
   

   4. 1440

   
   
   

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   Specific speed, Ns =	N√Q
   	H3/4

   
   

   =	1440 × √0.464
   	753/4

   
   = 38

   Correct Option: C

   Specific speed, Ns =	N√Q
   	H3/4

   
   

   =	1440 × √0.464
   	753/4

   
   = 38

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64. Water flows at a depth of 0.1m with a velocity of 6m/s in a rectangular channel. The alternate depth is

1. 1. 0.30 m

   
   
   

   2. 0.40 m

   
   
   

   3. 0.86m

   
   
   

   4. 0.81m

   
   
   

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   We find conjugate depth (answer for alternate depth not in options)
   

   Fr1 =	V1	=	6	= 6.06
   	√gy1		√9.81 × 0.1

   
   

   yz =	y1	[− 1 +√1 + 8Fr1²]
   	2

   
   

   =	0.1	[− 1 +√1 + 8 ×(6.06)²]
   	2

   
   = 0.81 m

   Correct Option: D

   We find conjugate depth (answer for alternate depth not in options)
   

   Fr1 =	V1	=	6	= 6.06
   	√gy1		√9.81 × 0.1

   
   

   yz =	y1	[− 1 +√1 + 8Fr1²]
   	2

   
   

   =	0.1	[− 1 +√1 + 8 ×(6.06)²]
   	2

   
   = 0.81 m

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65. Water flows at a rate of 10m³ /s in a rectangular channel 3 m wide. The critical depth of flow is

1. 1. 1.13 m

   
   
   

   2. 2 m

   
   
   

   3. 1.45 m

   
   
   

   4. 1.04 m

   
   
   

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   Critical depth, yc =		Q2		1/3
   		gB2

   
   

   =		102		1/3	= 1.04m
   		9.83 × 32

   Correct Option: D

   Critical depth, yc =		Q2		1/3
   		gB2

   
   

   =		102		1/3	= 1.04m
   		9.83 × 32

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