How can you find displacement given initial position, velocity, and time?

[csingham]

Homework Statement

xi=2.0
ti=0

i know the acceleration is -2.0 @ t=3 using the change v/ change t (rise over run)
the vx@ t=3 is two
and t=3
so i need to find the position of x
so i pluged in the formula x= xi+vt+1/2vt2 and I get 11..but I'm way off

Homework Equations

see above

The Attempt at a Solution

tried a few times working from going from the initial x all the way and I get 11 again.

Am I not entering in the sig figs right or am i way off?

I just found this forum and love it!

 

[Redbelly98]

That equation is for constant acceleration only.
The acceleration changes in this problem, so that equation will not work.

How do you get displacement from velocity in general?

 

[csingham]

That equation is for constant acceleration only.
The acceleration changes in this problem, so that equation will not work.

How do you get displacement from velocity in general?

i figured it out
I wasn't using the right vi

got me on the right path thanks!