A car of mass $m=1000\text{ kg}$ is moving with a velocity $v=20\text{ m/s}$. What is its kinetic energy $K$?

Solution

1. Use the formula $K=(1/2)m{v}^2$.
2. Substitute the given values $m=1000\text{ kg}$ and $v=20\text{ m/s}$.
3. Calculate $$\begin{array}{rl}K& =(1/2)\times 1000\times (20{)}^2\\ & =500\times 400\\ & =200,000\text{ J}\end{array}$$.
4. Convert to kilojoules: $200,000\text{ J}=200\text{ kJ}$.
5. Hence the answer is (B).