Question
A pump on the ground floor of a building can pump up water to fill a tank of volume 30 m3 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?
Solution
Given,
Volume of the tank, V = 30 m3
Time of operation, t = 15 min Volume of the tank, V = 30 m3
= 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,
P0 =
= 
= 30 × 103 × 9.8 ×
= 13.067 × 103 W
For input power Pi,, efficiency η, is given by the relation,
η =
= 30% Pi =
= 0.436 × 105 W
= 43.6 kW, is the electric power consumed by the pump.
