71. A jet of water, of cross-sectional area 0.005 m^{2} strikes a flat plate normally with a velocity of 15 m/s. If the plate is moving with a velocity of 5 m/s in the direction of jet and away from the jet, what is the force exerted by the jet on the plate?

- 0.50 N
- 250 N
- 0.25 N
- 500 N

72. A horizontal water jet with a velocity of 10 m/s and cross-sectional area of 10 mm^{2} strikes a flat plate held normal to the flow direction. The density of water is 1000 kg/m^{3}. The total force on the plate due to the jet is

- 10 N
- 100 N
- 1N
- 0.1 N

73. Jet ratio (m) is defined as the ratio of

- Diameter of the jet of water to diameter of the Pelton wheel
- Velocity of vane to velocity of the jet of water
- Velocity of flow to velocity of the jet of water
- Diameter of Pelton wheel to diameter of the jet water

74. Study of impact of jets and of velocity triangles is based on Newton’s law which states: Force = mass x acceleration. For practical applications, the following features are emphasized.

- Change of velocity takes place in time duration.
- Rather than the “mass’, the ratio of ‘weight’ and ‘g’ is used.
- Change of velocity normal to the direction of the impacting inflow is also relevant to the computations.

Which of the above are correct?

- i and ii only
- i and iii only
- ii and iii only
- i, ii and iii

75. Water is supplied from a height of 5.2 m at the rate of 100 lps to a hydraulic ram that delivers 7 lps to a height of 24 m above the ram. The head loss at the supply pipe is 0.2 m and the delivery pipe has a loss of 1.0 m. The efficiency of the ram is

- 22.8 %
- 29.8%
- 35.0%
- 39.6%

76. A turbine develops 500 kW power under a net head of 30 m. If the overall efficiency of the turbine is 0.83, the discharge through the turbine is nearly

- 3.5 m
^{3}/s - 3.0 m
^{3}/s - 2.5 m
^{3}/s - 2.0 m
^{3}/s

77. A rectangular plate, weighing 5 kg is suspended by a hinge on the top horizontal edge. The centre of gravity G of the plate is 10 cm from the hinged end. A horizontal jet of water of area 5 cm^{2}, whose axis is 15 cm below the hinge, impinges on the plate with velocity V m/sec. In this condition, the plate deflects from the vertical by 20° (sin 20° = 0.34, cos 20° = 0.94). What will be the jet velocity? Take g = 10 m/sec^{2}.

- 4.9 m/sec
- 5.2 m/sec
- 5.5 m/sec
- 5.7 m/sec

78. Constant efficiency curves are also known as

- Newton curves
- Pelton curves
- Muschel curves
- Kaplan curves

79. In the inlet part of the jet impinging on a Pelton bucket, the velocity of whirl V_{w1} is equal to

- absolute velocity of jet at inlet V
_{1} - relative velocity of jet at inlet V
_{r1} - zero
- none of the above

80. A hydraulic turbine has a discharge of 3 m^{3}/s when operating under a head of 15 m and a speed of 500 rpm. If it is to operate under 12 m of head, the rotational speed will be

- 600 rpm
- 559 rpm
- 447 rpm
- 400 rpm