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Homework Help: Elastic vs. Completely Elastic?

  1. Nov 30, 2013 #1
    1. The problem statement, all variables and given/known data

    A 2.4kg ball falling vertically hits the floor with a speed of 2.5m/s and rebounds with a speed of 1.5m/s. The impact or "collision" described in this problem is:

    a. completely elastic
    b. completely inelastic
    c. elastic
    d. inelastic

    2. The attempt at a solution

    As I understand it, the collision in this problem is "inelastic". However, the answer choices make a distinction between "completely elastic" and "elastic" collisions. Since there are no elastic collisions on the macroscopic scale, this cannot be a "completely elastic" collision. Yet, since some macroscopic collisions are approximated as elastic collisions, this might count as an "elastic" collision.

    Is the distinction between elastic and completely elastic collisions a legitimate one, or is it there just to throw me off? How would you answer this question?

  2. jcsd
  3. Nov 30, 2013 #2


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    I think it's there just to throw you off. A collision is either elastic or not. On the other hand, an inelastic collision isn't necessarily completely inelastic, so it makes sense to make a distinction.
  4. Nov 30, 2013 #3
    Thank you!
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