A pump raises 100 kg of water through 10 m in 20 seconds. Taking g as 10 m per second squared, its power output is

Explanation

The work done is mgh, that is 100 multiplied by 10 multiplied by 10, giving 10,000 J, and dividing by 20 seconds gives 500 W. Forgetting to divide by the time leaves the 10,000 distractor, which is the energy rather than the power. The pump's input power would be higher than this, since no machine is fully efficient.