# Homework Help: Tennis Ball Collison

1. Apr 8, 2016

### Of Mike and Men

1. The problem statement, all variables and given/known data
A 0.060 kg tennis ball, moving with a speed of 2.50 m/s has a head on collision with a 0.090 kg ball initially moving toward it with a speed of 1.00 m/s. Assuming a perfectly elastic collision, what is the speed and direction of each ball after the collision?

2. Relevant equations
m1v1 + m2v2 = m1v1' +m2v2'

v1-v2 = v2' - v1'

3. The attempt at a solution

I drew my positive x-direction to the right. Thus, ball 1 is going to the right prior to the collision and ball 2 is going to the left prior to the collision.

v1' = (m1v1 + m2v2 - m2v2') / m1

v1' = (0.06(2.5)-0.09-0.09v2')/(0.06)
v1' = (0.06 - 0.09v2')/0.06
v1' = -1.5v2'

v1-v2 = v2' - v1'
2.5+1 = 2.5v2'
v2' = 1.40
1.40 m/s to the right

v1' = v2' - v1 + v2
v1' = 1.4 - 2.5 - 1
v1' = -2.1
2.10 m/s to the left

Does this look correct?

2. Apr 8, 2016

### PeroK

You could check whether momentum is indeed conserved in your solution.

3. Apr 8, 2016

### Of Mike and Men

Duh. Thanks. :)