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Homework Help: Problem with Pressure Force

  1. Jan 20, 2005 #1
    I've got a "dilemma" here about Pressure Force:
    " Containers with different volumes but with the same areas at the bottom are filled with water of equal mass. Will the Pressure Force vary according to containers?"

    First of all I guess Pressure Force must be equal to the Weight [W] of water which is same for all containers W=mg=F , but on the other hand F=PxS=dghS=dgV (P-pressure, S-area at the bottom, d-density of liquid , V-volume of container) and it varies due to the volume of container.

  2. jcsd
  3. Jan 20, 2005 #2

    Doc Al

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    Staff: Mentor

    pressure depends on depth

    The pressure at the bottom of the container depends only the depth (h) below the surface of the water (ignoring atmospheric pressure): [itex]P = \rho g h[/itex]. So what matters is the height of the water in each container. Does the water reach the same height in each container?

    (The question is a bit ambiguous, since no mention is made of the shape of the containers.)
  4. Jan 20, 2005 #3
    The problem asks about Pressure Force (not Pressure) which causes pressure P=F/S S-Area
  5. Jan 20, 2005 #4


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    Science Advisor

    Since the areas of the bottoms are equal, the only thing that can vary the pressure at the bottom of the containers is the height the liquid rises in each container as Doc Al already said. The height that the level rises will be dependent on the containers' geometries.

    BTW..."Pressure force" is a horrible term to use. You're either interested in the pressure or the force applied.
  6. Jan 20, 2005 #5
    I'm interested in Force applied.
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