Question

Find the average force needed to accelerate a car weighing 500 kg from rest to 72 km/h through a distance of 25 m.

Answer 1

$$\begin{gathered} \text{Given}: \\ \mathrm{Mass}\mathrm{of}\mathrm{the}\mathrm{car},m=500\mathrm{kg} \\ \mathrm{Initial}\mathrm{velocity}\mathrm{of}\mathrm{the}\mathrm{car},u=0 \\ \mathrm{Final}\mathrm{velocity}\mathrm{of}\mathrm{the}\mathrm{car},\nu =72\mathrm{km}/\mathrm{h}=20\mathrm{m}/s \\ a=\frac{\left({\nu }^2-u^2\right)}{2s} \\ a=\frac{400}{50}=8\mathrm{m}/s^2 \end{gathered}$$

Force needed to accelerate the car,
$\mathrm{F}=ma=500\times 8=400\mathrm{N}$