Solving Manometer Problems - Pressure at Point B

[adam112]

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 I am getting is 18196.73 Pa, but I am not including p(roh)m in the equation.

I hope what I am 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.

 

[chemisttree]

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?)

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).

 

[nelzonjohn]

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?

 

[pmsrw3]

I'm having trouble with the 'roh' part of p(roh).

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.

 

[Redbelly98]

Just FYI, this thread is 3 years old.