A force of $F=10\text{ N}$ acts on a body of mass $m=2\text{ kg}$ for $t=5\text{ s}$. If the body starts from rest, what is the work done by the force?

Solution

1. Calculate acceleration using $$\begin{array}{rl}a& =F/m\\ & =10/2\\ & =5{\text{ m/s}}^2\end{array}$$.
2. Calculate final velocity using $$\begin{array}{rl}v& =u+at\\ & =0+5\times 5\\ & =25\text{ m/s}\end{array}$$.
3. Calculate work done using $$\begin{array}{rl}W& =\Delta K\\ & =(1/2)m{v}^2\\ & =(1/2)\times 2\times (25{)}^2\end{array}$$.
4. Hence the answer is (D).