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Homework Help: Perfectly inelastic collision and inelastic collision

  1. Oct 11, 2011 #1
    1. The problem statement, all variables and given/known data

    Two gliders move toward each other on a frictionless linear air track.

    Glider 1, mass = 0.5kg , velocity = 2m/s (to the left)
    Glider 2, mass = 0.3kg , velocity = 2m/s (to the right)

    After collision, glider 2 moves away (to the left) with final velocity of 2m/s.


    The question I want to ask is that, I read up on wikipedia, saying perfectly inelastic collision will result in the two objects sticking together and moving with a same final velocity.

    However in this question, I found out the final velocity for glider 1 to be v = -0.4m/s, which doesn't support what Wikipedia has since glider 2 moves to the left with 2 m/s. So I'm thinking maybe the question given is NOT a perfectly inelastic collision, can anyone clear my doubts about this?

    2. Relevant equations

    m1v1 + m2v2 = m1u1 + m2u2

    3. The attempt at a solution

    substituting masses and velocities into the above equations will get me v1 = -0.4 m/s
  2. jcsd
  3. Oct 11, 2011 #2
    The question directly states, if I understand you correctly that,
    Which implies that, once one of them has started to move separately, you can no longer consider it as a "perfectly" inelastic interaction between them. Rather, there could be a loss of kinetic energy due to other factors, but not such that would prompt them to coalesce.
    I hope that helps,
  4. Oct 11, 2011 #3
    Collision is not perfectly inelastic.
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