A lawyer seeks your advice in one of his cases. The question is whether a driver was exceeding a `45 km//hr` speed limit before he made an emergency stop, brakes locked and wheels sliding. The length of skid marks on the road was 5 m. The policeman, assuming that maximum deceleration of the car would not exceed the acceleration of a freely falling body `(10 m//s^(2))`, arrested the driver for speeding What is your opinion ?

Answer

The policeman was wrong in arresting the driver as the speed of car was `= 10 m//s = 36 km hr (lt 45 km//hr)` when breaks were applied

Explanation

As stopping distance `s = (u^(2)//2a)`,
`u = sqrt(2as) = sqrt(2 xx 10 xx 5) = 10 m//s`