A car moving aling a straight highway with speed of ` 126 km h^(-1)` is brought to a stop within a distance of ` 200 m`. What is the retardation of the car (assumed uniform ) ans how doest it take fro the car to stop ?

Explanation

Initial velocity, `u=126 km h^(-1)=(126xx5)ms^(-1)`
`=35ms^(-1)`
Final velocity v=0, s=200m
Using `v^(2)-u^(2)=2as`
`(0)^(2)-(35)^(2)=2xxaxx200`
Therefore, `a=(-35xx35)/(2xx200)`
or `a=-(49)/(16)=-3.06ms^(-2)`
As we know, `v=u+at`
`0=35-(49)/(16)xxt`
or `t=(35xx16)/(49)=11.3` s.