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Homework Help: Conservation of linear momentum!

  1. Jan 9, 2010 #1
    1. The problem statement, all variables and given/known data

    Two cars 1 and 2 moving against each other collides.There are no external forces acting on them.

    2. Relevant equations

    conservation of linear momentum:
    m1*v1+m2*v2 =(m1+m2)v12

    3. The attempt at a solution
    I have solved the problem but my question is how come they have a common speed after the collision?I dont understand this part can someone clarify it please.
  2. jcsd
  3. Jan 9, 2010 #2
    The equation you wrote is the one used when the two objects stick together when they collide, so after the collision there is only one object with a mass of m1+m2. This is called a perfectly inelastic collision. You can't use that equation if the objects bounce off each other.
  4. Jan 9, 2010 #3
    thanks a bunch mikelepore!
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