Question

A car is moving with a velocity of $80\text{m/s}$ and it takes $20\text{s}$ to stop after the brakes are applied. Calculate the force exerted by the brakes on the motorcar if its mass along with the passengers is $1000\text{kg}$.

• A. $4000\text{N}$
• B. $2000\text{N}$
• C. $1500\text{N}$
• D. $1000\text{N}$

Answer 1

The correct option is A $4000\text{N}$

From,

$v=u+at$

$a=\frac{v-u}{t}=\frac{0-80}{20}=-4{\text{m/s}}^2$

So, force applied by the brakes,

$F=ma=1000\times (-4)=-4000\text{N}$

Hence, option $\left(A\right)$ is the correct answer.