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Homework Help: Use mercury barometer to fing height of building

  1. Nov 29, 2005 #1
    A mercury barometer reads 700.0 mm on the roof of a building and 715 mm on the ground. Assuming a constant value of 1.29 kg/m3 for the density of air, determine the height of the building.
    .
    My setup was finding the difference in the pressures for mercury and get 15 mm Hg
    Then use Hg density = 136000 to get a pressure using P=pgh
    So P will equal 1999200
    then subtract atmosphere pressure and divide the result by 12.642 (pg)
    But the answer is wrong... Where did I go astray?
     
  2. jcsd
  3. Nov 30, 2005 #2

    Fermat

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    I haven't checked anything else, but the specific gravity of mercury is 13.6, so its density is 13.6 times greater than water, so density of mercury is 13.6*10^3 = 13,600 kg/m^3.
    You have 10 times that value, 136,000, or that a typo ??
     
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