Question

An engine lifts $2250$ litres of water per minute from a well $20m$ deep. If $25$ % energy of the engine is wasted, the power to be given to the engine must be (Take $g=9.8m/s^2$)

• A. $29400W$
• B. $9800W$
• C. $7350W$
• D. $13067W$

Answer 1

The correct option is B $9800W$

$1$ litre of water weighs $1$ kg
So, mass $m=2250kg$
$h=20m$
$t=60sec$
Effective power $=\frac{75p}{100}$, where $p=$ actual power

$g=9.8$ $m/s^2$

$\frac{75p}{100}=\frac{mgh}{t}$

We get, $p=9800W$