Question

A car having a mass of 1000 Kg is moving at a speed of 30 meters/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

Answer 1

The correct option is D 6 seconds

Given,

Final velocity, $v=0$

Initial velocity, $u=30m{s}^{-1}$

Force = mass x acceleration

$F=ma$

$\text{a}=\text{F}/\text{m}=-5000/1000=-5\text{m}{\text{s}}^{-2}$

From the First equation of motion,

$v=u+at$

$0=30+(-5t)$

$0=30-5t$

$5t=30$

$t=30/5$

$t=6$

Hence, after$6\sec$ car will stop.