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Basic question from well check the handle

  1. Sep 16, 2006 #1
    I'm involved in a little debate, and I'm looking for an answer to this ignant question:

    If I've got two objects of equal density but differing mass, let's say a 1 pound rock and a 1000 pound rock, and I throw them at 100mph over a surface such as dirt/grass, achieving equal height and contact angle upon impact with each object, will they bounce the same distance? (for the sake of argument we'll assume this is in a vacuum)

    I understand that the larger rock will achieve proportionately greater gravitational potential energy, and therefore proportionately greater kinetic energy, but it seems to me that the larger rock would also expend a greater amount of that energy displacing the earth upon contact than would the smaller, and would therefore generate less reactive energy (I'm sure that's a totally ignorant way to phrase it) to once again propel it skyward.

    Thanks for helping out a Dumbass5000.
  2. jcsd
  3. Sep 16, 2006 #2
    heh, grass and dust, are too complicated to be explained by a theory easly.
    lets say you have a surface which has no friciton your rocks.(though i think that friction would roughly give the same answer)
    also lets say that the surface is hard, and cannot be deformated.
    and lets say that the rocks are perfect spheres.

    in such conditions, the rocks whould act like a mirror, the angle you drop the rock on the surface, is the same as the angle it will move after the collusion, and the velocity before and after would be conserved.

    but i made lots of assumptions... maybe too much of them, but i dont think a simple theory could explain unsimmetric systems...
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