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Water, having a density of 1000 kg/m3, leave from a nozzle with a velocity of 10 m/s and the jet strikes a bucket mounted on a Pelton wheel. The wheel rotates at 10 rad/s. The mean diameter of the wheel is 1 m. The jet is split into two equal streams by the bucket, such that each stream is deflected by 120°, as shown in the figure. Friction in the bucket may be neglected. Magnitude of the torque exerted by the water on the wheel, per unit mass flow rate of the incoming jet, is

Water, having a density of 1000 kg/m3, leave from a nozzle with a velocity of 10 m/s and the jet strikes a bucket mounted on a Pelton wheel. The wheel rotates at 10 rad/s. The mean diameter of the wheel is 1 m. The jet is split into two equal streams by the bucket, such that each stream is deflected by 120°, as shown in the figure. Friction in the bucket may be neglected. Magnitude of the torque exerted by the water on the wheel, per unit mass flow rate of the incoming jet, is Correct Answer 3.75 (N.m)/(kg/s)

Velocity of Pelton wheel = ω  × r = 0.5 x 10 = 5 m/sec

Torque = ρQ(v-u) (1+cos θ)×R

Torque/mass = (v-u) (1+cos θ)×R = (10-5) × (1+cos 60) × 0.5

= 3.75 Nm/(kg/s)

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