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Energy Violation Puzzle - The use of Negative Buoyancy to run a turbine

  1. Jun 11, 2007 #1
    I was just swimming with a floating board for the pool, and came up with a thought.

    What would happen if you had two tubes one filled with air, and the other one filled with water. If you could somehow get an object less than half the density of water to fall down the tube with the air and go to the bottom of the other tube to displace water, couldn't the buoyant force exceed -1 times the force of gravity on the object? I posted an image on Wikimedia to illustrate this:

    http://commons.wikimedia.org/wiki/I...use_of_Negative_Buoyancy_to_run_a_turbine.gif

    If it could run a turbine with this, it would clearly violate the law of conservation of energy. But apparently, a nonconservative force is involved (i.e. gravity). Clearly, there would be a better mechanism for the "water lock" than a carousel, but this is what I came up with.

    So I need to know soon, WHERE is the catch (assuming all leakage problems are handled correctly)? Something doesn't make sense.
     
  2. jcsd
  3. Jun 11, 2007 #2

    russ_watters

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    Staff: Mentor

    I don't understand your diagram, but what I'm wondering is how you push the object into the tank of water against the water pressure?
     
  4. Jun 11, 2007 #3

    Danger

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    I'm not sure what you mean by the inclusion of a 'non-conservative force'. While gravity might initially drive the mechanism, you have to fight that gravity in order to restore it. It's a losing game.
     
  5. Jun 11, 2007 #4
    There must be water to be displaced. By looking at the top of the diagram, the water should only rise a fraction of the object's height. The difference must be similar to the volume of the item and the carousel itself (when the carousel is open). If the carousel has holes like that in a movie reel, then it is a matter of opening and closing the gates (the bottom one first). As for the energy to deal with the water pressure, assuming there is no more structural issue, then it is a matter of knowing whether there will be enough energy produced to overcome the energy to oppose water pressure. Elongating the column of water is not the solution, so one must make a vain attempt to try something else.

    One could split the column of water in half using a gate and gating it from the right tube while removing that portion some of its water in a seperate tank. In this way, it is easy to put the item into the water tube without having to deal with a lot of pressure on the carousel itself. Then that water can be reinserted followed by the opening of the gates.

    I believe there can be better solutions to the water pressure, but this is just my example.
     
    Last edited: Jun 11, 2007
  6. Jun 11, 2007 #5

    Danger

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    I'm sorry, man, but this makes absolutely no sense to me. You're bringing in so many convolutions that it's impossible for me to follow. Just take our word for it; it won't work. Your losses will always exceed your gains.
    (For one thing, what powers your 'gates'? That has to come from the mechanism itself, if you want it to be a closed system.)
     
  7. Jun 11, 2007 #6
    The power demand depends on how much water it is going to displace. If it is paper thin, then not much power is necessary, since it could basically slice through the water like a knife or dagger. By using strong materials the energy consumption should reduceable. The energy may be reduced close to that needed to refresh the tank with new water as well as moving the water at the bottom around (see diagram again), assuming that the all gates use neglible power and the carousels are light.

    http://commons.wikimedia.org/wiki/I...use_of_Negative_Buoyancy_to_run_a_turbine.gif

    I'm still not sure what would ultimately crossover the energy produced by the strong negative bouyancy as the gates, if made of good material, should solve the pressure problem.

    To summarize I will list what needs to be powered:
    • The first carousel
    • The second carousel
    • The water from the first carousel to the second
    • Gate A close
    • Gate B close
    • Gate for the water tank
    • The water from the second carousel to the water tube
    • Bottom gate for the carousel
    • Top gate for the carousel
    • Gate B open
    • Gate A open
    • The water from the water tube to the second carousel
    • The water from the second carousel to the first carousel
    • Water from the outside
    • Pushing the item back into the air tube

    in fact... I give up....
     
    Last edited: Jun 12, 2007
  8. Jun 12, 2007 #7

    russ_watters

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    You may want to google and peruse what you get for "buoyancy perpetual motion machine" - they are one of the most common types of perpetual motion machines and have been around in similar forms for hundreds of years. None of them work. Here's a good link with several examples: http://www.lhup.edu/~dsimanek/museum/unwork.htm
     
  9. Jul 9, 2007 #8
    I think the failure of this machine will be the ability of the buoyant float to rise over the top of the column and drop down.
     
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