Water falls from a height of 60 m at the rate of 15 kg/s to operate a turbine. The losses due to frictional force are 10% of the input energy. How much power is generated by the turbine? ($g=10 m/s^2$)

(1) 10.2 kW
(2) 8.1 kW
(3) 12.3 kW
(4) 7.0 kW

Solution

Loss in PE per sec. $=15 \times 10 \times 60 W$

Due to 10% loss, 90% of the above is converted into electric power.

So, power generated $=0.9 \times 15 \times 10 \times 60 = 8100 W = 8.1 kW$

Answer: (2)