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

We are given : `u = 126 km h ^(-1) = ( 126 xx 1000)/( 60 xx 60) = ms ^(-1) = 36 ms ^(-1) implies v = 0, s = 200 m`
Using relation : `v ^(2) - u ^(2) = 2 as`
` 0- (35) ^(2) = 2 a xx 200 or, a = ( - (35) ^(2))/( 2 xx 20)t implies t = ( 35 xx 16)/( 49) = (80)/(7) = 11. 43 s.`