Question

What is the average braking force required of a 1200kg car in order for it to come to rest from 60km/h in a distance of 25m

Answer 1

Vi = 60 km/h (1 h/3600 s)(1000 m/km)

v = Vi + a t
0 = Vi + a t
t = -Vi/a

d = Vi t + (1/2) a t^2

25 = Vi (-Vi/a) + (1/2)a (-Vi/a)^2

25 = -Vi^2/a + (1/2)Vi^2/a
25 a = -(1/2)Vi^2

Answer 2

the kinetic energy it possesses