Question

A car of mass $2,000kg$ is lifted up a distance of $30m$ by a crane in $1minute$. A second crane does the same job in $2minutes$. The power supplied by second crane is:

• A. $4900W$
• B. $9800W$
• C. $19600W$
• D. $980W$

Answer 1

The correct option is A $4900W$

Here, the work done by first crane, $W=$ potential energy $=mgh=2000\times 9.8\times 30=588000J$

As the second crane does same job, the work done by second crane is also equal to $W$.

The power supplied by second crane , $P=\frac{W}{t}=\frac{588000J}{2\times 60s}=4900W$