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Velocity and momentum?

  1. Mar 7, 2010 #1
    1. The problem statement, all variables and given/known data

    A 24,000 kg box car travelling north at 2 m/s collides with an 18,000 kg box car. Upon collision the two box cars lock together. What is the velocity of the 18,000 box car before the collision if after the collision the two box cars are traveling south at 1 m/s?

    2. Relevant equations

    MaVai + MbVBi = MaMaf + MbVbf

    3. The attempt at a solution
     
  2. jcsd
  3. Mar 7, 2010 #2

    lightgrav

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    what does "locked together" mean ? (show this on your "after" diagram)
     
  4. Mar 7, 2010 #3
    like the cars combined
     
  5. Mar 7, 2010 #4

    lightgrav

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    so, what is v_a,f ? ... what is v_b,f ?
     
  6. Mar 7, 2010 #5
    mass of a, velocity of a initial etc
     
  7. Mar 7, 2010 #6

    lightgrav

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    don't you know _numerical_values_ for the velocities afterward ?
     
  8. Mar 7, 2010 #7
    It is a case of a complete inelastic collision,the two carts will move together with a common velocity.
    m1v1 +m2(-v2)=(m1+m2)v
     
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