Question

A car travelling at a speed of 29.8 km hr-1 brakes and travels a distance of 0.02km before it comes to a complete stop. Find the time taken for the car to come to rest

Answer 1

$u=29.8\space km/h\\v=0\space km/h\\s=0.02\space km$

From Newton's laws of motion,

$\Rightarrow v^2-u^2=2as\\\Rightarrow a=\dfrac{-u^2}{2s}\\\Rightarrow a=-22,201\space km/h^2$

$v=u+at$

$\Rightarrow t=\dfrac{-u}{a}=0.00134\space hr=4.83\space s$

t = 4.83 s