A car moving along 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), and how long does it take for the car to stop ?

Explanation

Here, `u=126" km "h^(-1)=(126 times 1000)/(60 times 60)ms^(-1)`
`=35ms^(-1), v=0, S=200m, a=?`
We know
`v^(2)=u^(2)+2as`
`O=(35)^(2)+2 times a times 200` (Or)
`a=(-(35)^(2))/(2 times 200)=(-49)/(16)`
`" "=-3.06ms^(-2)`
As v = u + at
`" "0=35+((-49)/16)t` (Or)
`t=(35 times 16)/49=80/7=11.43s`