# Homework Help: Momentum of ball bouncing off wall

1. Oct 11, 2011

### aszymans

1. The problem statement, all variables and given/known data
A racquet ball with mass m = 0.247 kg is moving toward the wall at v = 12.4 m/s and at an angle of θ = 32° with respect to the horizontal. The ball makes a perfectly elastic collision with the solid, frictionless wall and rebounds at the same angle with respect to the horizontal. The ball is in contact with the wall for t = 0.063 s.

2. Relevant equations
What is the magnitude of the change in momentum of the racquet ball?

3. The attempt at a solution
I found the initial P already and am not sure if I should use the (delta)P= F(net)* (delta)t and use 1-d kinematics to find acceleration or how exactly to begin.

2. Oct 12, 2011

### grzz

Since the collision is assumed to be perfectly elastic, try using conservation of KE.

3. Oct 12, 2011

### grzz

Then find the change in momentum.

4. Oct 12, 2011

### HallsofIvy

Momentum is a vector quantity. The component of momentum parallel to the way will not change. The component of momentum perpendicular to the way is multiplied by -1.