A powered flood barrier rises vertically from the road. During a test, the barrier mechanism is supplied with 60 kJ of energy and transfers 15 kJ of energy to the thermal energy stores of the mechanism and its surroundings.
The mechanism operates at the same efficiency when it raises a barrier of mass 600 kg through a vertical height of 2.0 m at constant speed. Its input power is 4.0 kW.
Gravitational field strength is 10 N/kg.
Calculate the efficiency of the barrier mechanism.
Calculate the time taken to raise the barrier.