Question

A car is moving on a straight horizontal road with a speed of $72kmph$. If the coefficient of kinetic friction between the tyre of the car and the road is $0.5$, then find the minimum distance, within which the car can be stopped.

• A. $72m$
• B. $40m$
• C. $30m$
• D. $20m$

Answer 1

Answer: (B)

$40m$

From FBD, $ma=f=\mu N=\mu mg$
or $a=0.5\left(10\right)=5m/s^2$
by using $v^2-u^2=2aS$, we will get,
$0-(\frac{72\times 1000}{3600}{)}^2=2(5)S$
or $400=10S$
$\therefore$ Distance ,$S=40m$.