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Compressed chamber

  1. Mar 8, 2007 #1
    Just thinking here. What would happen if you had two pieces of something that connect perfectly and form a chamber of air inside. Then you took all the air out to make a perfect vacuum. Now if you were to pull the sides would it break apart. I don't understand how there would be a perfect vacuum inside that would hold the unit from seperating. If there is no air then it should be impossible to pull it apart right?
  2. jcsd
  3. Mar 9, 2007 #2


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    Staff: Mentor

    Not impossible. What holds them together is the air pressure outside of them pushing them together.
  4. Mar 9, 2007 #3
    I still don't understand how the inside of it could possibly expand. There is nothing to expand? Maybe I don't fully understand what a vacuum really is.
  5. Mar 9, 2007 #4
    Expansion doesn't matter here.

    When there is a closed chamber then there will be an inside pressure and an outside pressure.

    The outside pressure will apply force to hold the chamber together.
    The inside pressure will apply force to take the chamber apart.

    Wether the chamber will come apart or stay together becomes a contest between the outside and inside pressure.

    The inside pressure can be helped by pulling on the chamberhalves.

    Once Fpull + Finside > Foutside the chamber will break.

    http://www.ap.stmarys.ca/demos/content/fluids/magdeburg_hemispheres/magdeburg_hemispheres.html [Broken]
    Last edited by a moderator: May 2, 2017
  6. Mar 9, 2007 #5


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    Staff: Mentor

    Since a vacuum is just empty space, it doesn't matter what size it is.

    Again, what most people get wrong about a vacuum is that they think it somehow pulls on things. Since it is just empty space, how can it be pulling on anything?
  7. Mar 9, 2007 #6
    Thanks you guys.
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