Question

A crane is used to lift 1000 kg of coal from a mine 100 m deep. The time taken by the crane is 1 hour. The efficiency of the crane is 80%. If $g=10m{s}^{-2}$, then the power of the crane is

• A. ${10}^{4}W$
• B. ${10}^{5}W$
• C. $\frac{{10}^4}{36\times 8}W$
• D. $\frac{{10}^5}{36\times 8}W$

Answer 1

The correct option is D $\frac{{10}^5}{36\times 8}W$

$Powersupplied=\frac{mgh}{t}$
$Powerusedbycrane=\frac{mgh}{t}\times \frac{100}{80}$
$=\frac{1000\times 10\times 100}{3600}\times \frac{100}{80}=\frac{{10}^5}{36\times 8}W$