Question

An engine pumps up $100 \,kg$ of water through a height of $10\, m$ in $5 s$. Given that the efficiency of engine is $60 \%$. If $g=10\, ms ^{-2}$, the power of the engine is

• A. 3.3 kW
• B. 0.33 kW
• C. 0.033 kW
• D. 33 kW

Answer 1

Answer: (A)

Power is the rate at which a force does work.
Efficiency of engine, $\eta=60\%$
Thus, power $=\frac{\text { work } / \text { times }}{\eta}=\frac{100}{60} \times \frac{m g h}{t}$
Given, $m=100\, kg , h=10 \,m , t=5\, s$ and $g=10\, ms ^{-2} .$
Hence, power $=\frac{100}{60} \times \frac{100 \times 10 \times 10}{5} $
$=3.3 \times 10^{3} \,W$
$=3.3 \,k W$