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Manometer problems.

  1. Jan 28, 2008 #1
    Hi all, I really need some help with the following question,

    I have to find the pressure at point B, within the manometer.
    height A=0.71m
    height B=200mm
    p(roh)=882 kg/m^3
    p(roh)m=13784 kg/m^3 (is this the density of the gas?)
    Pressure at point A=156850Pa

    I have tried using the following equation: P1-P2=pg(h2-h1), is this correct?

    The answer im getting is 18196.73 Pa, but im not including p(roh)m in the equation.

    I hope what im trying to ask makes sense.

    If anybody can help, and maybe push me in the direction of a few websites, it would be mostly appreciated.
  2. jcsd
  3. Jan 29, 2008 #2


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    Not unless you think a cubic meter of the gas weighs about 14 metric tons! Sounds more like mercury ('m' = mercury?) to me....
    I'm having trouble with the 'roh' part of p(roh).
  4. Jul 22, 2011 #3
    what kind of manometer is that?is it a differential type? you mean the specific density p(roh)m? what element is p1 and p2? are they both h20?
    Last edited: Jul 22, 2011
  5. Jul 22, 2011 #4
    I'm guessing that, in the original problem, it's just a rho, and adam112 used a p because it looks like a rho, then put rho in parens to clarify (achieving, unfortunately, the opposite).

    adam112: Do you have a picture?

    13784 kg/m^3 is definitely the density of mercury, as chemisttree suggests. I'm not sure what the 882 kg/m^3. It would be about right for, say, ethanol, and is way too high for a gas. (And usually in a problem of this type the density of any gases would be negligible.) But without more info, I don't know why there would be two liquids involved.
  6. Jul 25, 2011 #5


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    Just FYI, this thread is 3 years old.
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