An engine pumps 400 kg of water through height of 10 m in 40 s. Find the power of the engine if its efficiency is 80% (Take ,g =10 `ms^(-2)`).

Explanation

Work done by engine against gravity
`W=mgh=400xx10xx10=40kJ`
Power used by engine `=W/(Deltat)`
`=(40xx10^(3))/(40)W=1kW`
If power of the engine is P, then
`Pxx(80)/(100)=1kW`
`impliesP=(1000xx100)/(80)Wor(100)/(80)kW=1.25kW`