Solving Manometer Problems - Pressure at Point B

  • Thread starter adam112
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You're probably not going to get an answer. In summary, the conversation discusses finding the pressure at point B in a manometer, given the heights of A and B, and the densities of water and possibly mercury. The equation P1-P2=pg(h2-h1) is mentioned, but it is unclear if it is correct. The conversation also mentions confusion about the use of "p(roh)" and the possibility of using a picture for clarification.
  • #1
adam112
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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.
 
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  • #2
adam112 said:
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).
 
  • #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:
  • #4
chemisttree said:
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.
 
  • #5
Just FYI, this thread is 3 years old.
 

1. What is a manometer?

A manometer is a scientific instrument used to measure the pressure of a fluid, usually a gas or a liquid, in a closed system.

2. How does a manometer work?

A manometer works by comparing the pressure of the fluid in the system to a reference pressure. This is typically done by using a U-shaped tube filled with a liquid, such as mercury or water, where one end is connected to the system and the other end is open to the atmosphere. The difference in the height of the liquid in the two arms of the tube is used to calculate the pressure.

3. What is the pressure at point B in a manometer?

The pressure at point B in a manometer is the pressure of the fluid in the system, which is being measured. It can be calculated by using the difference in liquid height in the two arms of the U-tube and the density of the liquid.

4. What factors can affect the accuracy of a manometer reading?

The accuracy of a manometer reading can be affected by several factors, including the type of liquid used, the temperature of the liquid, the level of precision in measuring the liquid height, and any external forces acting on the system.

5. How can I solve manometer problems to find the pressure at point B?

To solve manometer problems and find the pressure at point B, you will need to use the equation P = ρgh, where P is the pressure, ρ is the density of the liquid, g is the acceleration due to gravity, and h is the difference in liquid height in the two arms of the U-tube. Plug in the values and solve for pressure at point B.

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