Question

Calculate the work required to be done to stop a car of $1500kg$ moving at a velocity of $60km/h$.

Answer 1

Step 1: Given data

Mass, $\mathrm{m}=1500kg$

Initial velocity, $v_i=60km/h=\left(60\times \frac{5}{18}\right)m/s=16.67m/s$

Final velocity, $v_f=0km/h=0m/s$

Step 2: Calculate the work required

The change in kinetic energy $\mathrm{k}$ is calculated below:

$$\begin{gathered} \mathrm{k}=\frac{1}{2}m{v_{\mathrm{i}}}^2 \\ \mathrm{k}=\frac{1}{2}\times 1500\times {\left(16.67\right)}^2 \\ \mathrm{k}=\frac{1}{2}\times 1500\times 277.89 \\ \mathrm{k}=208417J \end{gathered}$$

The kinetic energy of the car, when it comes to rest $=0J$

$Workdoneonobject=changeinkineticenergy$

$$\begin{gathered} =208417–0 \\ =208417J \end{gathered}$$

Hence, the work required to stop the car is $208417J$