PHSYICS QUESTION>>>>AVERAGE ACCELERATION?

Question

A new model BMW can start from rest and travel

400 m in 16 s.

a What is its average acceleration during this time?

working would be appreciated thanks

Answer 1

dx=.5*a*t^2

dx=.5*a*t*t (1)

v=a*t (2)

(1) and (2)

dx=.5*v*t

400=.5*v*16

v=50m/s

(2) --> a=v/t

a=3.125m/s^2

Answer 2

Technically there's not enough information to answer the question-- the car could accelerate for half the distance and decelerate for half the distance in which case the average acceleration is zero.  However if you assume the acceleration was constant:

d = 1/2 a t^2

a = 2 d / t^2 = 800m / (256 s^2) = 3.125 m/s^2