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Overunity questions

  1. Dec 17, 2014 #1
    I know perpetual motion machines typically break the third law of thermodynamics...due to friction losses.
    So let's use a flywheel, spinning in a magnetic field, as an actual real world example of a working perpetual motion machine with zero losses to friction, or if not zero then practically zero, I mean maybe a magnetic flywheel would stop after 10,000 years or something but that's nit picking in my book. The wheel just keeps in motion until the energy is taken out. A magnetic flywheel is a great battery but not an overunity device obviously...
    However the fact it spins indefinitely doesn't seem to qualify as perpetual motion? Why is that.
    I'm just mentioning a magnetic flywheel as an example of a device that doesn't break any laws of physics but to any reasonable minded person it is perpetual motion.
    So what about overunity? An object in motion has greater kinetic energy than a inanimate object. So a falling boulder has more energy than a still one. Depending on the hight the boulder drops from, the greater the energy it has.
    Yet gravity is a force and supposedly not a form of energy, even though hydroelectric dams wouldn't function without gravity. So if gravity isn't energy then what's powering the hydroelectric dam? And if gravity can amplify the amount of kinetic energy in a falling object then that object possesses more kinetic energy depending on it's relation to gravity.
    But I've never heard anyone say gravity creates energy or adds more energy to objects in motion.
    Surely if an objects falls from a greater hight and has greater kinetic energy the added energy must be due to gravity adding that energy? Isn't this overunity? Because a still boulder only has potential energy, but how can you measure the potential energy of a boulder? I mean you can measure the potential energy of a lump of coal because we can compare it to other lumps of coal and their burn rate... There is some uniformity there but an object can virtually contain any amount of energy depending on how fast it's moving. We also know objects move incredibly fast in the vacuum of space, making objects like comets perpetual motion objects and IMO overunity objects.
    So here is my question on overunity.
    If a spaceship took a boulder into space and we calculated the amount of energy needed to do that.
    Then when in space the spaceship pretty much drifted far far out into deep space, using no more that a push on it's booster rockets. And we calculated the amount of energy needed to drift maybe a hundred light years etc or more. Then if the ship turned around and pushed the boulder on a trajectory back to earth, with nothing more than a slight nudge.
    Depending on the distance the ship drifted with no significant additional energy expended on travelling in space, when the boulder would hit earth as an asteroid strike, surly the impact would release many thousands times more energy than it took for the spacecraft to get the boulder into space. Isn't this obvious fact, proof that energy can be added and overunity exists. More energy comes out of the boulders impact than it took to get the boulder into space. So where did the extra energy come from?
     
  2. jcsd
  3. Dec 17, 2014 #2

    davenn

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    we don't discuss that subject here. please read the PF rules

    cheers
    Dave
     
  4. Dec 17, 2014 #3
    I did read the rules with all due respect. All I basically want to know is if we took a boulder into space and pushed It back to earth, the energy released from the impact could easily far exceed the energy it took to take the boulder into space and push it back to earth. So that means energy was added from somewhere. I just want to know from where.
     
  5. Dec 17, 2014 #4

    DaveC426913

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    Maybe I can sneak this in before the thread gets locked. :)
    Lots things do this. Atoms, asteroids, planets.

    It's not perpetual motion per se; it's the intent to extract useful work from it that's erroneous.

    Nope. Same energy.

    Use a simpler model. Pick up a rock. Drop it.
     
  6. Dec 17, 2014 #5

    russ_watters

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    1. Newton's 1st law says that objects can move forever, so it is a misnomer that "perpetual motion" is impossible, just perpetual motion machines.
    2. "Overunity" means more energy out than in. That's the first law of thermodynamics, not the third. You should read the wiki on the different categories of perpetual motion machines: http://en.wikipedia.org/wiki/Perpetual_motion
    3. Hydroelectric dams harness a solar powered steam cycle. http://en.wikipedia.org/wiki/Water_cycle

    Anyway, yeah, we don't discuss that here, but I think I have you covered with those answers...
     
  7. Dec 18, 2014 #6

    Drakkith

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    To get this cleared up:

    The work required to lift the boulder is equal to the work done by gravity on the boulder as it falls. By performing work, you gave energy to the boulder in the form of potential energy when you lifted it against gravity. This potential energy was transformed into kinetic energy as the boulder fell. Just before impact the boulder's kinetic energy is equal to the potential energy it had right before you dropped it. Upon impact the boulder's kinetic energy is transformed into heat and other forms of energy. (Kinetic energy of the rocks flying away from the impact point, deformation of the ground, etc) At no point is energy created, it is only transformed from one form to another.
     
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