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Perpetual motion machines - gravity an unconventional source?

  1. Sep 17, 2009 #1
    This example is highlighted in the Wikipedia definition of perpetual motion.

    Machines which are claimed not to violate either of the two laws of thermodynamics but rather to generate energy from unconventional sources are sometimes referred to as perpetual motion machines, although they are generally considered not to meet the standard criteria for the name. By way of example, it is possible to design a clock or other low-power machine, such as Cox's timepiece, which runs on the differences in barometric pressure or temperature between night and day. Such a machine has a source of energy, albeit one from which it is impractical to produce power in quantity.

    Is gravity considered an unconventional source of energy?
    Or can a perpetual motion machine take advantage of gravity?

  2. jcsd
  3. Sep 17, 2009 #2
    What is it with all of the perpetual motion threads? Perhaps we could write a perpetual forum for them that just posts to itself all by itself forever and ever and never cosumes energy. LOL

    By the way, the discussion of perpetual motion machines is not allowed on this forum.

  4. Sep 17, 2009 #3
    haha yeah sorry, im new. where do i put it?
  5. Sep 17, 2009 #4


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    Staff: Mentor

    No, he means not allowed on PF at all.

    In any case, that's irrelevant, since gravity is not an energy source. Gravity is like a spring sitting on your floor...it just sits there doing nothing. It doesn't expend energy just being a spring. If you drop a weight on it, it'll store some potential energy until you lift the weight off of it, but that's it.
  6. Sep 17, 2009 #5


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    Staff Emeritus
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    Gold Member

    No, gravity is not a unconventional source of energy.

    No, gravity cannot be used to run a perpetual motion machine.

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