Originally Posted by **Palilth** A ball is traveling at 3m/s then bounces off of a tennis racket and returns at 2m/s. If the ball is in contact with the racket for 12ms, what is the average acceleration?
I converted 12ms to **0.012s**. Then I listed what is known in the problem. The initial velocity is **3m/s **and the final velocity is **-2m/s.**
I know the equation for acceleration is **Vf-Vi/Tf-Ti.**
But the answer that I get is **-417m/s^2.**
The question is multiple choice and none of the answers match this.
What am I doing wrong here? |

I agree with you.

Quick point: $\displaystyle v_f - v_i / t_f - t_i$ is incorrect. You need parenthesis: $\displaystyle (v_f - v_i)/(t_f - t_i)$. You probably think I'm being picky about the notation (along with another post I made to you) but you have to get the notation right in order to speak clearly about it.

-Dan