A car travelling along a highway must uniformly reduce its speed to12 m/s in 3.0 s.?

Question

It travels 60 m during this time.
a) What is the car’s average acceleration?
b) What is its initial velocity?
.

Answer 1

a) 5.33 m/s^2 [Backward]
b) 27.99 m/s [Foreward]

Answer 2

v = v0 + at
s = v0t + (1/2)at^2
v0 = v - at
s = (v - at)t + (1/2)at^2
s = vt - at^2 + (1/2)at^2
s = vt - (1/2)at^2
a = 2(vt - s)/t^2
a = 2(12*3 - 60)/3^2
a = 2(- 24)/9
a = - 16/3 m/s^2
v0 = 12 - (- 16/3)(3)
v0 = 12 + 16 = 28 m/s