Question

The power of a crane is 6.25 kW. How much mass of coal it can lift in 1 hour from a mine of 100 m depth? The efficiency of the crane is 80% and $g=10m{s}^{-2}$.

• A. 1800 kg
• B. 18,000 kg
• C. 180 kg
• D. 1,80,000 kg

Answer 1

The correct option is A 1800 kg

$Power=\frac{\text{Work Done}}{time}=\frac{mgh}{t}$

Efficiency $=0.8$
${10}^3\times 6.25\times 0.8=\frac{m\times 10\times 100}{60\times 60}$
$m=1800kg$