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Shape of hydraulic piston thought experiment

  1. Mar 14, 2009 #1
    Typical hydraulic pistons are flat simple surfaces.

    What if one had a T-shaped or a upside down U-shaped piston? i.e. the "leg" of the T would be in the liquid submerged protruding down.

    Some of the horizontal piston surface would be at a great depth, while some piston surface would be at depth zero (surface contact at underside of the top part of the "T").

    Would the bottom of the piston contacting the liquid at a certain depth be fighting hydrostatic pressure at that depth?

    Liquids tend to "level out" when under the influence of gravity so I wonder if the bottom leg horizontal surface portion of the "T" piston is "pressed up" on as the liquid tries to level out. However the liquid really cannot level out since that would create a vacuum at surface liquid/piston contact point (depth 0).

    Just something that popped up in my mind as an interesting thought experiment. It is as if there would be an invisible vacuum glue holding everything in place at the topmost (surface) liquid/piston contact surface area at the underside of the T, to counterbalance the liquid trying to level out. That is, if indeed the piston just stays there in equilibrium. Well imagine the letter "T" as a piston, instead of a simple underscore "_" as a piston.

    Of course there would be other factors such as.. well what size of piston is on the other side of this hydraulic system, etc. ? Well just consider one T piston with an open system on the other end (column of water), or even two equal T equal pistons, one on each end in a closed system. Either way, it is interesting to "try" and cancel out the forces on the T piston(s) and liquid so that everything is in equilibrium. I say "try", because, I am having a bit of a hard time visualizing how/why things cancel out with regards to the lowest portion of the piston (bottom of T) touching the hydrostatic pressurized liquid at a depth.
    Last edited: Mar 15, 2009
  2. jcsd
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