Question

A car is moving with a speed of $100km{h}^{-1}$. If the mass of the car is $950kg$, then its kinetic energy is

• A. $0.367MJ$
• B. $3.67J$
• C. $3.67MJ$
• D. $367J$

Answer 1

The correct option is A

$0.367MJ$

Step 1: Given data

Speed of the car, $v=100km{h}^{-1}=\left(100\times \frac{5}{18}\right)m{s}^{-1}=\frac{250}{9}m{s}^{-1}$.

Mass of the car, $\mathrm{m}=950kg$.

Step 2: Calculating kinetic energy

Kinetic energy $k$ is calculated as,

$\begin{array}{rcl}k& =& \frac{1}{2}\mathrm{m}{v}^2\\ & =& \frac{1}{2}\times 950kg\times {\left(\frac{250}{9}m{s}^{-1}\right)}^2\\ & =& 366512.346J\\ & =& 0.367MJ\left[1MJ={10}^{6}J\right]\end{array}$

The kinetic energy of the car is $\begin{array}{rcl}& & 0.367MJ\end{array}$

Hence, option (a) is correct.