Using acceleration to find distance traveled

[swede5670]

Homework Statement

A car accelerates from 18 m/s to 45 m/s in 12 s. Assume constant acceleration.
What was its acceleration? How far did it travel?

I know that the acceleration is 2.25 m/s/s but I'm not sure how to go from acceleration to distance traveled.

Homework Equations

I'm guessing that its this one
vf^2 = vi^2 + 2a * ChangePosition

The Attempt at a Solution

(vf^2 - vi^2)/2a = change in position

So I get 45^2 - 18^2 / 24 which equals 70.875 meters. When I submitted the problem I got the acceleration right but I screwed up the change in position.

 

[ussfletcher]

d = 1/2 at^2

 

[Mentallic]

You accidentally substituted the time instead of the acceleration into your rearranged equation:

$$\Delta x=\frac{v_{f}^{2}-v_{i}^{2}}{2a}$$

 

[Mentallic]

d = 1/2 at^2

To use this formula, the entire equation will need to be put to use. i.e.

$$s=ut+\frac{1}{2}at^{2}$$
s = displacement
u = initial velocity