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

initial velocity `u = 126 xx (5)/(18) = 35 m//s`,
`s = 200` m
From equation of motion `v^(2) = u^(2) + 2as`
`rArr 0 = (35)^(2) + 2a xx 200 rArr a = -3.06 m//s^(2)`
`therefore ` retardation is 3.06 ` m//s^(2)`
`v= u + at, 0 = 35 - 3.06t`
`t = 11.4 sec`.