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Homework Help: Another Hydrostaic force Problem

  1. Dec 20, 2009 #1
    This is a problem right out of the text of my calculus book. So I actually have the work, but I'm confused about something the did.

    Problem: Find the hydrostatic force on one end of a cylindrical drum with radius 3 ft. if the drum is submerged in water 10 ft deep.

    I attached a diagram

    Pressure can be defined:

    p=density, d=distance below the surface

    [tex]P=pgd=\delta d[/tex]

    The area of the ith strip is:

    [tex]A_i=2\sqrt{9-(y^*_i)^2}\Delta y[/tex]

    The average distance below the surface is:

    [tex]d_i=7-y^*_i[/tex]

    Then when they write the pressure, they give:

    [tex]\delta_i=62.5(7-y^*_i)[/tex]

    The implies that [tex]pg=62.5[/tex].

    The density of water is [tex]p=62.4 lb/ft^3[/tex]

    http://en.wikipedia.org/wiki/Density_of_water

    Gravitational acceleration is [tex]32.174 ft/s^2[/tex]

    So how does [tex]\delta d_i=pgd_i=62.5(7-y^*_i)[/tex] ? Is this an error? It seems that they accidently neglected to account for gravitational acceleration.
     

    Attached Files:

  2. jcsd
  3. Dec 20, 2009 #2

    ideasrule

    User Avatar
    Homework Helper

    Yeah, it's an error.
     
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