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Homework Help: Hydrostatic Pressure - Theoretical Scenario

  1. Jul 4, 2011 #1
    I have come to understand the basics of Pascal's Principle/Hydrostatic pressure, but there is one scenario I am looking for help with.

    If I have a piston at the bottom of a chamber of water, and I want to push the piston up to lift the water, I understand that I need to exert a greater PSI on the Piston than the PSI the water is exerting on the surface of the Piston.

    However, let's say that (as indicated by the attached picture) I have a Piston that is attached to the ground, and the container of water is "free standing"... meaning the container of water can collapse onto the Piston (thereby displacing the water upwards).

    How do I know if the container would indeed fall on the Piston and thereby displace the water?

    Aren't the walls (and thereby the Piston) exerting the same PSI on the water as the water is exerting on the walls (and Piston)? If so, who wins?

    Intuitively, I want to say that no matter what... in any scenario such as I pictured... the container of water will fall on top of the Piston every time... but my intuition has proved wrong many times before.

    Is it really possible that the PSI of the water at the bottom of the container could hold the container up and prevent it from collapsing onto the Piston?

    Are there scenarios where the container of water will hold itself up? Or will it collapse every time?

    Thanks for any help. This is one where I don't really know how to even begin doing the calculation.

    Attached Files:

  2. jcsd
  3. Jul 4, 2011 #2
    Here is a response I received to the same question/example on another forum. It helps a little, but am still hoping someone can be more detailed.

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