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Homework Help: Pressure as a function of depth

  1. Apr 15, 2007 #1
    1. There is a 16.8 m tall oil-filled barometer. The barometer column is 80.0% filled w/ oil when the column of a mercury barometer has a height of 722mm Hg. If the density of mercury is 1.36 x 10^4 kg/m^3, what is the density of oil?

    2. Relevant equations
    P=Po + pgh

    3. The attempt at a solution

    so the oil barometer has 13.44 m of oil. I know density of the mercury and the height of the mercury barometer. Do i have to set abs. pressure of oil to that of mercury and go from there? Any feedback would be appreciated.
  2. jcsd
  3. Apr 15, 2007 #2
    Is there a picture that goes along with this problem? Its worded in a way that confuses me (and you too, no doubt)?

    Assuming the most straightforward situation,

    Pa+Xrho*g*h=Pa+Hgrho*g*h. the Pa for ambient or atmospheric pressure cancel. G divides out. Does that help?
  4. Apr 15, 2007 #3
    yeah it is worded a bit weird. Ok, so what's Xrho and Hgrho. Do u mean the density of the oil and mercury by that? And also for the depth of the oil, do i use 16.8 or 13.44 which is the height of the oil in the barometer?
    Last edited: Apr 15, 2007
  5. Apr 15, 2007 #4
    yep I should bite the bullet and download Latex, but yes rho(density) for oil and Hg. And assuming these are separate physical systems, the height for oil would be 13.44
  6. Apr 15, 2007 #5
    thx bro appreciate it.
  7. Apr 15, 2007 #6
    No prob, keep coming back ;-D
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