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Homework Help: Two objects colliding & sticking together, what is their final speed?

  1. Dec 7, 2008 #1
    1. The problem statement, all variables and given/known data

    Two freight cars, each with a mass of 2.5 multiplied by 10^5 kg, collide and stick together.
    One was initially moving at 3.4 m/s and the other was at rest. What is their final speed?

    2. Relevant equations

    3. The attempt at a solution
    (2.5*10^5)(0-3.4)= -850,000
    = -8.5 * 10^5 m/s
  2. jcsd
  3. Dec 7, 2008 #2
    The main thing you can use in the problem is conservation of momentum:


    This equality is a result of the completely inelastic collision. The question asks you to solve for v'.
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