Question

A car moving on a straight highway with speed of $126$km/hr, is brought to stop within a distance of $2$. What is the retardation of the car(assumed uniform) and how long does it take for the car to stop?

Answer 1

$u=126\times \frac{5}{18}=35m/s$

$s=2m$

$v^2=u^2-2as$

$v=0$

$u^2=2a_d.s$

$35\times 35=2\times a_d\times 2$

$a_d=306.25m/s^2$

$v=u-a_{d}t$

$v=0$

$u=a_{d}t$

$t=\frac{35}{306.25}=0.114s$