Question

a motorist traveling at 72 kilometre-per-hour on citing a stop road signs apply the brakes such that under constant deceleration the car is brought to stop within a distance of 50m.what is magnitude of the deceleration

Answer 1

$v=\sqrt{2|a|s},\implies$

$|a|=\frac{v^2}{2s},$

$a<0,$

$a=-\frac{20^2}{2\cdot 50}=-4~\frac m{s^2}.$