An electric motor takes 20 s to lift a box of mass 20kg to a height of 1.5 m. Find the amount of work done by the machine and hence find the power of the electric motor.

**Answer**:

Work done,

W = mgh = (20)(10)(1.5) = 300J

Power,

\begin{gathered}
P = \frac{W}
{t} \hfill \\
P = \frac{{300}}
{{20}} = 15W \hfill \\
\end{gathered}