Question

An engine pumps up $100\text{kg}$ of water through a height of $10\text{m}$ in $5\text{s}$. Given that the efficiency of the engine is $60\%$, what is the power of the engine? (Take $g=10m/s^2$)

• A. $33\text{kW}$
• B. $3.3\text{kW}$
• C. $0.33\text{kW}$
• D. $0.033\text{kW}$

Answer 1

The correct option is B $3.3\text{kW}$

Work done to pump the
the water to a height of $10\text{m}$$=mgh=100\times 10\times 10$
$=10000\text{J}$
Power required $=\frac{\text{work}}{\text{time}}=\frac{10000}{5}=2000\text{W}$
$\therefore$ Power delivered by the engine $=\frac{\text{Power required}}{\text{Efficiency}}=\frac{2000}{0.6}$
$=3.3\times {10}^3\text{W}$
$=3.3\text{kW}$