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Homework Help: Inelastic collision problem - What is the velocity?

  1. Feb 10, 2008 #1
    1. The problem statement, all variables and given/known data
    2 equal masses travel in opposite directions at equal speeds. They collide in a perfectly (inelastic) collision. Just after the collision their velocities are:
    B)equal to their original velocities
    C)equal in magnitude but opposite in direction of their original velocities
    D)less in magnitude and in the same direction as their original velocities
    E)less in magnitude and opposite in direction as their original velocities

    2. Relevant equations

    3. The attempt at a solution
    I believe that the answer is zero, because if they collide with equal mass, and equal velocity, which means they have the same momentum, then they must stop each other, an inelastic collision is where they stick to each other, so then it must be zero.

    I have 2 other questions just like this, expect one asks about a "perfectly elastic colllison" and another about a "collision that is between elastic and inelastic" ( i have no idea what that means..).

    An elastic collision is a "perfect scenario collision", so they must hit each other and bounce back at the same speed...so it would be B for that one?

    Thanks for taking time to read this long post, and please inform me if my logic isnt right..
  2. jcsd
  3. Feb 10, 2008 #2


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    Science Advisor
    Homework Helper

    1, Correct
    Perfectly elastic means no energy is lost.
    Inelastic collision doesn't necessarily mean they stick - it means that energy is lost (eg to heat)
  4. Feb 10, 2008 #3
    Well, it says "perfect inelastic collision" so im assuming they stick,thats what my books says.
    So, then for the inelastic collision the answer is A, but for elastic collisions the answer is B?
    Does any one know what the "collision between elastic and inelastic" means and can help me figure it out?
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