Q. A car having a mass of $1000\ kg$ is moving at a speed of $30\ metres/sec$. Brakes are applied to bring the car to rest. If the frictional force between the tyres and the road surface is $5000\ newtons$, the car will come to rest in
A) $5\ seconds$
B) $10\ seconds$
C) $12\ seconds$
D) $6\ seconds$
Explanation
(d) $v = u - at \Rightarrow t = \frac{u}{a}$ [As $v = 0$]
$t = \frac{u \times m}{F} = \frac{30 \times 1000}{5000} = 6\ sec$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.