A water pump pumps 3 kg of water every second from the bottom of a well to the top of the well 50 m above. If the pump uses 2000 W of electrical power to accomplish the task, what is the efficiency of the pump

70%

Explanation:

Power = work / time

P = mgh / t

P = (3 kg) (9.8 m/s²) (50 m) / (1 s)

P = 1470 W

Efficiency = power out / power in

e = 1470 W / 2000 W

e = 0.735

The efficiency of the pump is 0.735, or 73.5%.

Rounded to one significant figures, the efficiency is 0.7, or 70%.