Question

A motor pump-set of efficiency 80 % lifts 6000 litres of water per minute from a well 20 meters deep. If $g=10m{s}^{-2}$ then its input power is

• A. 20 kW
• B. 25 kW
• C. 16 kW
• D. 250 kW

Answer 1

The correct option is B 25 kW

Power supplied by the motor pump set $=\frac{\Delta (P.E)}{t}$

$=\frac{mgh}{t}$

$=\frac{\rho Vgh}{t}$ (where, $\rho$ is density and $V$ is volume of the water)

$=\frac{{10}^3\times 6\times {10}^3\times {10}^{-3}\times 10\times 20}{60}$

$=20\times {10}^{3}W$

Input power $=\frac{2\times {10}^3}{0.8}=25\times {10}^{3}W$