Question

A car of mass 1200 km moving at a speed of 36 km / hr was brought to rest in 20 m by applying brakes. What is the magnitude of constant braking force acting on the car?

Answer 1

mass = 1200 kg
speed = 36 km/hr =10 mls
distance travelled after braking = 20
retardation = -( u^2)/(2x)
= -(10*10)/ (2*20)
= -2.5 m/s^2
retarding force = mass *retardation
=1200*2.5
= 3000 N
= 3 KN