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Fun idea, the falling ball

  1. Oct 15, 2009 #1
    So i was thinking, if you drop a ball that has a bouncy property to it, it will travel half as high after the bounce, then in theory it will bounce half as high, and half, and half, and half but never reaches zero

    this is not true in reality though, because there of a loss of energy due to air resistance and stuff.

    just a fun idea :P
  2. jcsd
  3. Oct 15, 2009 #2
    The time intervals for each bounce reduce so their sum is convergent and finite: 1 +1/2 + 1/4 + 1/8 + ... = 2 or so.
  4. Oct 15, 2009 #3


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    If we didn't have to consider the ugly exigencies of reality, such as friction and inelastic deformation, the ball would not bounce half as high each time; it would bounce the same height each time, ad infinitum.

    As soon as you allow for inelastic rebound, you are opening the door to friction and energy loss. So why stop there?
  5. Oct 16, 2009 #4
    Another thing that is cool along the lines of what you had said, is an increased bounce every time :O

    so lets say that a bounce of .5 means it is times .5 for every bounce but what about 1.5! it would become infinitely faster until it broke from the walls of its containment and flew into space! - it could be a new rocket!

    sadly this is seamingly impossible
  6. Oct 16, 2009 #5


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    Well, yes.

    In order to bounce higher, it would have to have an energy source (either internal or external) and a mechanism for transferring that into propulsion. So far, our best bet is mixing LHy and LOx*.

    *OK, make your bagels & cream cheese jokes now....
  7. Oct 16, 2009 #6
    What an odd place to start -- my first post in this forum...

    Here's one possibility: http://www.gutenberg.org/etext/23153" (Gutenberg.org)
    Last edited by a moderator: Apr 24, 2017
  8. Oct 17, 2009 #7


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    Interesting. The Absent-Minded Professor written by Samuel W. Taylor hit the theatres in March 1961. The Big Bounce written by Walter S. Tevis was published in Galaxy mag in Feb. 1958.
    Last edited by a moderator: Apr 24, 2017
  9. Oct 17, 2009 #8


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    At some point this movement becomes smaller than the movement of the molecules due to thermal energy.
  10. Oct 19, 2009 #9
    You might want to look up Zeno's paradox, it deals with a similar problem of ever decreasing finite steps towards zero without ever actually getting there, With Zeno's it deals with 'time' as the quantity you are dividing up, so perhaps a better example of a paradox (well it is for me anyway because I imagine your ball example follows a non linear relationship due to real life losses, whereas with time it's not quite that simple to debunk)
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