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Homework Help: Easy problem that I'm a bit confused about.

  1. Mar 11, 2008 #1
    1. The problem statement, all variables and given/known data

    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.
    2. Relevant 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.
     
  2. jcsd
  3. Mar 11, 2008 #2
    Looks good to me.
     
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