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Elastic collision in 2-D?

  1. Mar 23, 2009 #1
    1. The problem statement, all variables and given/known data
    A hockey puck B rests on a smooth surface of ice and is struck by a second puck A , which was originally traveling at 40.0 m/s and which is deflected 30.0 degrees from its original direction. Puck B acquires a velocity at a 45.0 degree angle to the original direction of A. The pucks have the same mass.
    -Compute the speed of puck A after the collision.
    -Compute the speed of puck B after the collision.
    -What fraction of the original kinetic energy of puck A dissipates during the collision?

    2. Relevant equations



    3. The attempt at a solution
    This has got me really confused. I don't even know where to begin. I drew a diagram thought I was supposed to find the x and y components of A to get the final velocity of A and then change in A equals the negative change in B, but I'm not getting it. Please help!!
     
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  3. Mar 23, 2009 #2

    robphy

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    show more work...

    what diagram did you draw?
    what equations would you need to satisfy?
     
  4. Mar 23, 2009 #3
    My diagram shows puck A moving in the positive x direction at 40 m/s and colliding with puck B. After the collision puck A is deflected 30.0 degrees relative to the positive x axis at some final velocity. Puck B moves from rest to some final velocity 45 degrees relative to the negative x axis.
    I'm not exactly sure which equation(s) I need. I'm assume because the masses are unknown but equal, the equation change in velocity of A is equal to the negative change in the velocity of B.
     
  5. Mar 23, 2009 #4

    robphy

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    In general, what happens in a collision?
     
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