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When can we have perpetual motion?

  1. Mar 9, 2013 #1
    I was reading Feynman's lectures Vol I. There he says it is possible to have perpetual motion ideally. Considering everything is ideal what is the condition to have perpetual motion? For example if you take a weighing machine, is it possible to have perpetual motion for all weights on both panes or only for those for which the weighing machine balances?

    Thanks a lot
  2. jcsd
  3. Mar 9, 2013 #2

    Vanadium 50

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    He most certainly does not mean we can have "perpetual motion" in the usual sense of the word (which is a banned topic here) - a machine that continually produces energy.
  4. Mar 9, 2013 #3
    Ya I know that it's not possible and it's just for imagination purposes only. He even states on one sentence that balanced objects means perpetual motion. Does that perpetual motion is possible only for balanced weighing machines?

    Just for curiosity why is this topic (perpetual motion) banned?

  5. Mar 9, 2013 #4

    Doc Al

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    What's the exact reference?
  6. Mar 9, 2013 #5
    A few quotes from Feynman's Lectures Vol. I
    Those quotes are from chapter 4-2 - "Gravitational potential energy"

  7. Mar 9, 2013 #6


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    Because (i) there isn't one and (ii) such topics/discussions often attract crackpots.

    Please review the PF Rules that you had agreed to for a complete list of banned topics.

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