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Homework Help: Inelastic Collision

  1. Oct 20, 2006 #1
    A railroad car of mass 2.49 104 kg, is moving with a speed of 3.89 m/s. It collides and couples with three other coupled railroad cars, each of the same mass as the single car and moving in the same direction with an initial speed of 1.95 m/s.
    (a) What is the speed of the four cars after the collision?
    (b) How much mechanical energy is lost in the collision?

    Sorry, but I have no idea about this problem :(
     
  2. jcsd
  3. Oct 20, 2006 #2

    Doc Al

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    Staff: Mentor

    Hint: What is conserved in any collision?
     
  4. Oct 20, 2006 #3
    Momentum, so...

    2.49e4 * 3.89 + 3*2.49e4 *1.95 = 4*4.29e4 * V

    ?
     
  5. Oct 20, 2006 #4

    Doc Al

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    Staff: Mentor

    Right. Looks good, except for a typo. Once you solve for the final speed, you can figure out the initial and final kinetic energies and compare them.
     
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