In a hydroelectric power station, water falls at the rate of 2.0 × 105 kg s–1 through a vertical height of 215 m before driving a turbine.
(a) Calculate the loss in gravitational potential energy of the water each second. [3]
(b) Assuming that all this energy is transferred to kinetic energy of the water, calculate the speed of the water as it enters the turbines. [3]
(c) The water leaves the turbines at a speed of 8 m s–1. Calculate the maximum input power to the turbines. [2]
(d) The electrical output is 250 MW. Calculate the efficiency of this method of transferring gravitational potential energy to electricity. [2]
