The initial velocity(u) of the car is = 54km/hr = 15m/s
The final velocity(v) of the car is = 0 m/s
The time taken(t) by the car to come to rest = 90 seconds
We must find the acceleration(a) and displacement(s) covered by the car
From v = u+at .we find acceleration of the car .
By substituting in the equation we get
0 = 15 + a(90)
a = - 15/90
a = -1/6 m/s²
The displacement of the car is given by
v²-u² = 2as
0²-15² = 2*(-1/6)s
225 = (1/3)s
s= 225*3 =675 m.