A pump on the ground floor of a building can pump up water to fill a tank of volume 30m3 in 15 min. If the tank is 40 m above the ground, and the efficiency of the pump is 30%, how much electric power is consumed by the pump?

Volume of the tank, V = 30 m3
Time of operation, t = 15 min = 15 × 60 = 900 s
Height of the tank, h = 40 m
Efficiency of the pump, η = 30%
Density of water, ρ = 103 kg/m3
Mass of water, m = ρV = 30 × 103 kg
Output power can be obtained as:

Po=WorkdoneTime=mght
=30×103×9.8×40900=13.067×103W

For input powerPi , efficiency ηis given by the relation:

η=P0Pi=30%
Pi=13.06730×100×103
=0.436×105W
=43.6kW