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Work Energy Thm

  1. Apr 18, 2009 #1
    1. The problem statement, all variables and given/known data

    There are 2 identical boxes. One box is stationary. Another box is moving towards the other box at 6 m/s. After the collision what is the speed of the originally stationary box? Give a numerical answer in m/s.

    2. Relevant equations

    p=m1v1
    W=K2-K1

    3. The attempt at a solution

    so I would use conservation of momentum

    p1=p2
    m*6=m*v1+mv2

    and after this there's no way to solve for v2? I don't know what speed the orignally moving box will travel ???

    Thanks
     
  2. jcsd
  3. Apr 18, 2009 #2
    It seems that you are missing an important bit of information - was the collision elastic or inelastic? Or how much energy was lost (to friction) during the colission.

    With this bit of information, you can use the conservation of enrgy equation along with the conservation of momentum equation. You then have 2 equations with 2 unknowns (v1 and v2), and you can solve for them.
     
  4. Apr 18, 2009 #3
    thanks for the reply

    I forgot to mention that it was an elastic collision.

    Conservation of energy eqn? How do I do that?

    ty
     
  5. Apr 18, 2009 #4

    Doc Al

    User Avatar

    Staff: Mentor

    Set initial kinetic energy equal to final kinetic energy.
     
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