Question

A pumps lifts water from a lake to a large tank 20 m above the lake. How much work against gravity does the pump do as it transfers 5.0m^3 of water to the tank? One cubic meter of water has a mass of 1000 kg.

Answer 1

The work done by pump against gravity

$$W=mgh\\ =\rm 5.0*1000\:kg*9.8\: N/kg*20\: m=9.8*10^5\: J$$