Question

2. Driver of a car moving at 72 km/h takes 0.2 s to apply the brakes after finding a need for it. The driver finds that a child is crossing the road at a distance of 54 m from the car. What should be minimum deceleration of the car to save the child?​

Answer 1

Velocity u = 72x5/18
= 20 m/s


Distance covered before brake application

S= u x t

= 20x 0.2

=4m

Remaining distance =54m - 4m =50m

Deceleration = (v^2-u^2)/2S

= (0-20^2)/2x50

= - 4m/s2