Question

A car is moving with at a velocity if 45 km/hr. The driver applies the brakes and the car comes to rest in 3 second. What is its retardation? How far does it move before coming to rest?

Answer 1

Initial speed u = 45 km/h = 12.5 m/s,

Final speed v = 0 m/s,

time t = 3 s,

acceleration a.

v = u + at=> 0

= 12.5 + a(3)

a= -(12.5/3)

= -4.17 m/s^2.

Retardation = 4.17 m/s^2.

Distance travelled d = (1/2)(12.5)(3) = 18.75 m.