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Fluid statics

  1. May 8, 2017 #1
    1. The problem statement, all variables and given/known data
    I am trying to study for an exam and a section in the book on pressure on a plane is shown in the attached picture. I am trying to understand how equation15.16 was derived. I know normally the line of action is found using moments so this seems to be a short cut but I can'tunderstand how the book got to this equation. Any help would be muchappreciated. Thanks!

    2. Relevant equations

    3. The attempt at a solution

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  2. jcsd
  3. May 8, 2017 #2


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    Equation 15.16 is illegible. Please post it with a better picture. Also post the relevant equations and your bet attempt at solving or understanding what is going on.
  4. May 8, 2017 #3
    I don't believe the issue is that they took some clever shortcut as it is that they plain just didn't say anything about how they got there. I am sure they just found the centroid as the that is pretty easy and I can't imagine there being anything shorter.

    Write the pressure as a function of depth h and integrate

    ∫ h P(h) / ∫ P(h)

    from h1 to h2.
  5. May 9, 2017 #4


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    This is not an equation. An equation has two sides. Which side is this, what is the other side and what is the equation supoosed to represent?
  6. May 10, 2017 #5


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    Or even just looked it up... Centroid of a trapezoid.
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