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Homework Help: Elastic Collision Problem

  1. Mar 2, 2009 #1
    1. The problem statement, all variables and given/known data

    A 6 gram ball moving north at a rate of 3 m/s collides head on with an identical ball moving south at 2.0 m/s. The collision is elastic and the first ball moves south at 1 m/s. What is the velocity of the second ball?

    2. Relevant equations

    Law of conservation of momentum.

    3. The attempt at a solution

    The question makes no sense to me. According to my solution guide, the other ball moves off at 2.0 m/s. But of the collision is elastic, then no energy should be wasted. So...2.0m/s worth of energy from the first ball is sucked into an abyss? Can anyone shed light on this?
  2. jcsd
  3. Mar 2, 2009 #2


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    Science Advisor

    Yeah I don't know about this one. Energy's definitely not conserved using the given data. Chalk it up to a miswording?
  4. Mar 2, 2009 #3
    I hope so, or we're getting into magic rather than physics...thanks for confirming this...
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