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Homework Help: Fluid Mechanics: Differential Hg Manometer

  1. Sep 21, 2009 #1
    1. The problem statement, all variables and given/known data
    A differential mercury manometer is connected to pipe A containing gasoline (SG=0.65), and to pipe B containing water. Determine the differential reading, h, corresponding to a pressure in A of 20kPa and a vacuum of 150 mm Hg in B.

    2. Relevant equations
    Distance from pipe A to fill line is 0.3 m and distance from pipe B to other fill line is 03 m.

    3. The attempt at a solution
    I have done a few manometer problems before, however, I am not sure what to make of the "vacuum of 150 mm Hg in B". I do not know what this is implying to the problem?
    If someone could kindly explain I would be very grateful and will be able to complete the question.
  2. jcsd
  3. Sep 22, 2009 #2


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    Staff Emeritus
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    Homework Helper

    It sounds like they are talking about the pressure relative to 1 atm (760 mm Hg).

    So the "vacuum of 150 mm Hg" means an absolute pressure of (760-150) or 610 mm Hg.

    This probably means the 20 kPa pressure is really 1 atm + 20 kPa.
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