Need help with this question regarding kinematics.

Sep 2018
5
0
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?
 
Jun 2016
1,198
566
England
Could you post the other multiple choice options for us please?
This might let us identify what is missing from your analysis of the problem.
 

topsquark

Forum Staff
Apr 2008
2,978
631
On the dance floor, baby!
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