Acceleration?

Question

So this is the problem:
You are riding on the Demon rollercoaster. At T=1 second going down the 2nd hill, your car is traveling at a speed of 2 m/s. After 3 seconds, your car reaches the bottom of the hill travelling at 5 m/s. What is your acceleration?

So far I have:
a= ?
vf=5 m/s
vi=2 m/s
Would T= 4 seconds, or 1 second or 3 seconds?

Answer 1

T is the time it takes for it to happen. They tell you "after 3 seconds", so T is 3. Keep working, you're on the right track!

Answer 2

vf^2 = vi^2 +2aX
Assuming uniform(steady) acceleration, X = (vi+vf)/2 * t
= (2+5)/2 * 2
= 7m

So 5^2 = 2^2 +2a(7)

25-4 = 14a
21 = 14a
a = 3/2 m/s^2

Answer 3

Acceleration is the change in velocity over the change in time. So it would be (vf-vi)/(tf-ti)


(5-2)
-------- = acceleration
(3-1)