Question

A motor pump set of efficiency $80\%$, lifts $800$ litres of water in $19.6$ seconds over a head of $20m$. Its input power is (Take $g=9.8m/s^2$):

• A. $64kW$
• B. $40kW$
• C. $10kW$
• D. $196kW$

Answer 1

The correct option is C $10kW$

Since the efficiency of the pump is $80\%$, we can say, effective power of the pump is $\frac{80P}{100}$

$m=800kg,h=20m$ and $g=9.8$$m/s^2$

$t=19.6s.$

Putting these values into $0.8P=mgh/t$, we get,

$P={10}^{4}W=10kW$