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Motor which operate solely on magnet and gravity?

  1. Feb 18, 2009 #1
    I received an assignment from my professor which sounds like follow:

    "Suggest a motor which operates only on magnets and gravitational force."

    While I did make a search online and found some model which seems to work, I am sill a little skeptical (There are videos online, but none of them are authentic). Are there any design which full fills such requirement, and has been verified? I was told that such machine would not violate the 2nd Law of Thermodynamics because the magnet itself is the energy source. Can anyone verified / debunk this?

    Thanks in advanced.
  2. jcsd
  3. Feb 18, 2009 #2


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    Without any external energy input - it's going to be tricky.
    Otherwise it's quite easy.
    1, Attach plastic paddle wheel to electric motor.
    2, Stand above it
    3, Drop magnets onto paddle wheel.
    4, Motor turns - generates electricity
  4. Feb 18, 2009 #3


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    Gold Member

    You may try putting a permanent magnet on a Focault pendulum.
    As the pendulum precesses the magnetic interacts with the earth's magnetic field and adds kinetic energy!
  5. Feb 18, 2009 #4

    Ivan Seeking

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    It not only violates the second law, it also violates Ivan's law. :biggrin:

    Perpetual motion/free energy discussions are banned because it [such a motor] would violate the second law.

    There is a small amount of energy stored in the field of a magnet, but only a very little bit. And there is no way to switch it on and off as we would do for a motor using electromagnets, brushes, and a rotor.
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