1. The problem statement, all variables and given/known data This is a fairly straightforward question I'm sure. I have a ball. This ball has a mass of mass M. I throw this ball with a velocity v against a wall (perfectly along the x-axis (in the positive direction)). Now suppose the ball stays in contact with the wall for a time [tex]\Delta[/tex]t. Then the ball will rebound back perfectly along the x-axis (in the negative direction). 2. Relevant equations A.) What is the momentum of the ball [tex]\Delta[/tex]t/2 after originally making contact with the wall? B.) What is the tennis ball's momentum change between the time BEFORE it hits the wall to the time it is in CONTACT with the wall? C.) What is the tennis ball's momentum change between the time it is in CONTACT with the wall and AFTER it makes contact with the wall? 3. The attempt at a solution Well, for A.) I would say something like this: Firstly I would model the ball and wall as an isolated system. Secondly since it is moving perfectly along the x-axis I would then say: p=mv And according conservation of momentum I am lead to believe that the momentum of the ball at [tex]\Delta[/tex]t/2 is mv. But I am not confident. B.) Next I am lead to believe that the change in momentum BEFORE it hits the wall and while it's in CONTACT with the wall is 0 because of conservation of momentum. C.) I come to the same conclusion as in B.