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Do kinetic energy conserved in a 2 dimensional collision?

  1. Nov 12, 2012 #1
    Like the tittle suggests, do kinetic energy conserved in a 2 dimensional collision? Like when 2 metal balls collide. Thanks!
  2. jcsd
  3. Nov 12, 2012 #2
    Sometimes, when this happens we call it an elastic collision:

    Sometimes, though, this does not happen. In these cases we call the collision an inelastic collision:

    Nothing is ever perfectly elastic, because kinetic energy is not a conserved quantity, but there are lots of examples where, for all intents and purposes, kinetic energy is conserved. Two metal balls would be a good example of this, and the classic example are billiard balls. How elastic or inelastic a collision is depends primarily on the rigidity of the materials the objects are made from.
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