Question

A car moving along a straight highway with speed of $126km{h}^{-1}$ is brought to a stop within a distance of 200 m. What is the retardation of the car (assumed uniform), and how long does it take for the car to stop ?

Answer 1

$u=126km/h=126\times \frac{5}{18}m/s=35m/s$
$v=0$
$s=200m$
Newton's Equation of motion
$v^2-u^2=2as$
$0^2-{35}^2=2a\left(200\right)$
$a=-3.0625m/s^2$
Also
$v=u+at$
$0=35-3.06t$
$t=11.4s$