# Easy problem that I'm a bit confused about.

## Homework Statement

You have Joe and John playing catch in space. Joe throws the ball to John with a velocity of 7.5 m/s.

Given Variables
Joe's mass is 60.9 kg
John's mass is 79.8kg
Ball's mass is 6.5kg

Find:
A) Joe's velocity after he throws the ball.
B) John's velocity after he catches the ball.

## Homework Equations

Sum of the external forces = 0; Psys=0

For A, I used:
(Mass of ball+ Mass of Joe) (Velocity of Joe after he throws the ball) + (Mass of ball)(Velocity of Ball) = 0

I ended up with: Velocity of Joe after he throws the ball = - [(Mass of ball)(Velocity of ball)]/(Mass of Ball + Mass of Joe9)

After substituting in the numbers, the velocity of Joe is: -.72329 m/s

For B, I used:

(Mass of Ball)(Velocity of Ball) = (Mass of John + Mass of Ball)(Velocity of John after he catches the ball)

The Velocity of John after he catches the ball is: .56489m/s

Did I set this problem up properly?
Any suggestions or clarification would be greatly appreciated. Thanks.