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Homework Help: Horizontal force across a partition

  1. May 13, 2016 #1
    1. The problem statement, all variables and given/known data
    Find the horizontal force across the partition in a water tank with two compartments, one filled with water to x height and the other with water to y height. I've worked out the thrust acting on the partition as a result of density, height, gravity and average depth, so I have two horizontal vectors, with which to find the total horizontal force.

    2. Relevant equations

    3. The attempt at a solution
    (sum) Fx=(Force from oil) - (Force from water). Problem is I don't know which force is in which direction relative to the partition. The only solution I can see, which would make sense is adding the two forces together. Is this correct?
  2. jcsd
  3. May 14, 2016 #2

    Simon Bridge

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    I'm confused.
    You write,
    ... but "oil" is not mentioned in the problem statement, which says:
    ... just water on each side of the partition.

    Looking at those heights:
    Lets say y>x, then what else is in the tank at height h: y-x<h<y? What about when h>y?

    ... but your problem statement says:
    ... which direction is "horizontal"?
  4. May 14, 2016 #3
    The question says there is a tank which has a vertical partition across the width. There are two compartments in the tank, one contains water the other oil. I have worked out the hydrostatic force each liquid exerts on the partition. Now I have to find the 'horizontal force on the partition', Do I add the two forces together?
  5. May 14, 2016 #4
    Horizontal parallel to the base of the tank, normal to the vertical partition, I assume.
  6. May 14, 2016 #5
    Does the horizontal resultant force equal the difference between the two opposing forces?
  7. May 15, 2016 #6

    Simon Bridge

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    The resultant force is the vector sum of all the forces ... the horizontal resultant force is the horizontal component of the resultant force.
    In your case - where do the forces come from? Where do the forces act?

    I am making some assumptions about what the question is really asking ... technically the net horizontal force on the partition must be zero since it is not accelerating. I am guessing the question wants the net force due to the difference in pressure on each side.
    Last edited: May 15, 2016
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