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Atmospheric Pressure

  1. Oct 17, 2005 #1
    This is a problem i have in my homework and i want to learn how to do these and get them right so please dont just give me an answer lol

    The desity of the fluid in a tube is 850 kg/m cubic. THe pressure exerted by the atmospher is 1.013x10^5 Pa. What is the pressure P in the container?

    I hate the book we are using because i dont think it gets too detailed on what we should do.. it gives 3 examples and none of them are like it is on the problem set..

    its Physics An incremental Development SAXON and its our AP Physics book.
  2. jcsd
  3. Oct 17, 2005 #2


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    HINT: At any level in the fluid, the fluid supports the weight of all the fluid directly above it - plus the weight of the all the atmosphere directly above it.
  4. Oct 17, 2005 #3
    so how would i set this problem up? and thanks for the hint.. i didnt learn that in class so i added it to my personal notes :smile:

    the way i think im supposed to set this up is distance .21 m times 1.012x1065 x 850 kg/m cubic .. im thinking the density may be throwing me off though..
  5. Oct 17, 2005 #4


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    At depth D, the weight of the fluid above that level is [itex]\rho A D g[/itex] where A is the cross sectional area of the column and [itex]\rho[/itex] is the mass density of the fluid. The force bearing downward by the atmosphere is [itex]P_A \times A[/itex]. Those two forces are balanced by the pressure of the fluid at depth D: [itex]P_f \times A[/itex].

    You should be able to work it out from there! :)
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