Question

A car is running with a velocity of 72km/hr.if it is brought to rest suddenly by applying brakes by seeing a child 30 metre ahead on the road and bus stops at a distance of 20 metre,calculate the retardation of the car and the time taken by the car to come to rest.​

Answer 1

v*2-u*2=2as

0-400=40a

a=-10m/s*2

now,

t=v-u/a

t=0-20/-10

t=2sec