A car starting from rest accelerates. Uniformly for 5sec reaches a velocity of 12m.s-1.it then maintains this velocity for 4sec,after which the brakes are applied to bring the car to rest over a distance of 24m. 1.calculate the uniform acceleration experienced by the car in the first 5sec?

Answer 1

v = 0 + a t
12 = a (5)
a = 12/5

Is that the whole question? Surely they ask about the deceleration as well?
d = Vi t + (1/2) a t^2
so
24 = 12 t + (1/2) a t^2
v = Vi + a t
so
0 = 12 + a t

Answer 2

diagram