A pump can take out 7200 kg of water per hour from a well 100 m. deep. The power of pump, assuming its efficiency as `50%` will be

Explanation

`"Output power"=(mgh)/(t)=(7200xx10xx100)/(3600)=2000 W`
`"Efficiency" eta =("output power")/("input power")`
`"Input power"=("output power")/(eta)=(2000xx100)/(50)=4 kW`