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Pressure from mass without external gravity

  1. Apr 29, 2012 #1
    In this problem I consider no other gravity, no Earth, only mass and water. Mass of screw is very small and can be considered to 0. The black mass create pressure in water. The screw is put in water at a side, the screw turn only. The mass and water move up. Like no other gravity is present, we need 0 energy for move up the mass and the water. The screw turn with a torque in this case ? If yes, the pressure at bottom increase the weight to move ? But move a weight need 0 energy in theory (acceleration/deceleration). Like we can imagine a screw like a circle shape I think there is no torque so the pressure is not like water on Earth ?

    I think with a screw fixed and the water+mass turn around the screw and move up (or down) if the fact that part of screw create a force, in this case the water+mass has an acceleration ? Because the water+mass move perpendiculary to the forces, this don't need energy. But the pressure at bottom is greater. This case is also a problem with external gravity like on Earth.
     

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    Last edited: Apr 29, 2012
  2. jcsd
  3. May 5, 2012 #2
    nobody has an idea how pressure is in water ?
     
  4. May 5, 2012 #3

    Ken G

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    Gold Member

    We don't understand what you are asking. Perhaps choose a single question, and make it very clear, without such a strange example.
     
  5. May 5, 2012 #4
    ok, thanks, I try to be clear in my questions:

    1/ in my last drawing (one mass + water + helicoid), the pressure in water give a torque to the helicoid ?

    2/ The energy need to move the mass + water increase if the pressure give a torque ? I think because energy is conserved.

    Edit: 3/ So if pressure give force in the last case, this say in this new case (see drawing below) the water + mass move alone ? (the green part is fixed).
     

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  6. May 5, 2012 #5

    russ_watters

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    I'm sorry, but we're having a lot of communication problems here and honestly I don't think it is a language problem, but an idea problem: your ideas are just incoherent. Frankly, they all look like attempts at perpetual motion, but they aren't coherent enough to be sure. This one makes no sense:

    1. Is the water in a container?
    2. If there is no external gravity, how can there be any forces? Are you just looking at the gravitational forces between the parts?
    3. Screws are small - what is keeping the water from flowing past it?
     
  7. May 5, 2012 #6
    1/ yes, the water is in a container (can be a little greater than the volume of water)
    2/ no external gravity. Gravitation from mass M (mass below water), sure the pressure forces are small but exist. The mass M can be greater than I drawn, but I move the mass with water
    3/ imagine a side with gaskets, the relative position to the water from screw is always the same, because water move up and the screw turn only.

    NB in the second drawing the stem is not a screw it's a very long (infinite) part of material with or without mass. And the problem is the same with acceleration from magnetism or electrostatic I think.
     
    Last edited: May 6, 2012
  8. May 6, 2012 #7

    russ_watters

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    Are you applying a torque to the screw to turn it or assuming the water will make it turn?

    How can the water move "up" if it could just flow around the turning screw? Is the screw just moving the container?
     
  9. May 6, 2012 #8
    I don't apply a torque to the screw, I see a torque because the pressure below is greater than at top of the screw (if the pressure is like on Earth, a mass attrack and create pressure)

    The water don't move up alone, I move up the mass + water I don't see where is the force which move down the mass + water, this is the screw that give this force ?

    I see a torque on the screw which give energy, and I don't see the contrary force on the water+mass which compensate this energy.

    Maybe the second drawing is easier to understand, no torque, only forces, I see a force due to the pressure that want to move water+mass in a direction.
     
  10. May 6, 2012 #9

    russ_watters

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    Sorry, but there is no torque on the screw due to water pressure. you appear to me to be wasting your time looking for perpetual motion.
     
  11. May 6, 2012 #10
    ok, it's the same thing on the second drawing ?at right the force is not greater than at left ?

    1/ FR >FL ? if not why ?
    2/ FS1 and FS2 are perpendiculary to the movement, so they don't change energy I think ?
    3/ At top no force, because the water is attrack at bottom and the container can be greater than the volume of water
    4/ Mass attrack water but water attrack mass so no force on the system Water+Mass, if not why ?
     

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  12. May 7, 2012 #11
    I think I have find something easier to study for find my error. I use only the bottom of the water. I think it's possible to change mass to big magnet and water to small magnet balls, the study must be the same. Or use small springs with small balls where water is and attach these springs where the mass is. It's only a mechanical problem and it will be possible to find where is my error.
     

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