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Homework Help: Conservation of momentum on bike

  1. Jun 25, 2007 #1
    1. The problem statement, all variables and given/known data

    Tony (45kg) coasts on his bike (5kg) at a constant speed of 1 m/s, carrying a 5kg pack. Tony throws his pack forward, in the direction of his motion, at 5 m/s relative to the speed of bike just before the throw. What is the bike speed immediately after the throw?

    2. Relevant equations

    mv1 + mv1 = mv2 + mv2

    3. The attempt at a solution

    I combined Tony and the bike's mass together, 50kg. I then did
    (50)(1) + (5)(1) = (50)(v) + (5)(5) and solved for v. However that wasn't correct. Can somebody please tell me what I did wrong?

    Thank you so much!
  2. jcsd
  3. Jun 25, 2007 #2
    Please read the following carefully.

    Relativity is your friend. :wink:
  4. Jun 25, 2007 #3
    thanks so much! :)
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