Pressure diagram labelled incorrectly?

In summary: Ptotal = Patsurface + Pgauge holds true. However, he also clarifies that what is referred to as Pgauge is just the portion of the pressure due to the weight of the fluid itself. Therefore, the pressure at the bottom of the container would be the greatest. Additionally, Chet explains that it is the pressure of the fluid, not the volume, that counts. Finally, he defines gage pressure as total pressure minus ambient atmospheric air pressure. In summary, Chet clarifies the concept of gage pressure and explains that the equation Ptotal = Patsurface + Pgauge is still valid.
  • #1
needingtoknow
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Homework Statement



At the point specified in the diagram, isn't pressure coming from all directions, namely gauge pressure. So wouldn't some of the gauge pressure be used to counteract the effects from the atmospheric pressure. Doesn't this mean the equation Ptotal = Patsurface + Pgauge is wrong?
 

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  • #2
You are correct that at any point, the pressure is the same in all directions. But I believe you are misinterpreting the diagram. What they are calling Pgauge is just that portion of the pressure due to the weight of the fluid itself. So the equation holds.
 
  • #3
So but if it's only due to weight then by that saying wouldn't water at the bottom of the container have the greatest Pgauge because it is under the most fluid and the weight of a fluid is F = Pvg right so more volume = larger weight?
 
  • #4
needingtoknow said:
So but if it's only due to weight then by that saying wouldn't water at the bottom of the container have the greatest Pgauge because it is under the most fluid and the weight of a fluid is F = Pvg right so more volume = larger weight?
It's the pressure of the fluid, not the volume, that counts. But yes, at the bottom of the container the pressure due to the fluid is greatest. The pressure at any point below the surface is given by ρgh, regardless of volume.
 
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  • #5
All right great then that makes sense! Thank you very much!
 
  • #6
Gage pressure is defined as total pressure minus ambient atmospheric air pressure.

Chet
 

1. What is a pressure diagram and why is it important?

A pressure diagram is a graphical representation of the distribution of pressure within a particular system. It is important because it helps scientists and engineers understand how pressure is distributed and how it affects the behavior of the system.

2. How can a pressure diagram be labelled incorrectly?

A pressure diagram can be labelled incorrectly if the values or units on the axes are incorrect, if the labels are misplaced, or if the diagram does not accurately represent the actual pressure distribution in the system.

3. What are the potential consequences of an incorrectly labelled pressure diagram?

An incorrectly labelled pressure diagram can lead to incorrect interpretations and decisions about the system, which can result in equipment failure, safety hazards, or other negative consequences.

4. How can an incorrectly labelled pressure diagram be fixed?

An incorrectly labelled pressure diagram can be fixed by carefully reviewing the diagram and correcting any errors in the labels or values. It may also be necessary to redo the diagram if it does not accurately represent the pressure distribution.

5. How can scientists avoid incorrectly labelling pressure diagrams?

Scientists can avoid incorrectly labelling pressure diagrams by double-checking all labels and values before finalizing the diagram, using accurate and precise measurement tools, and consulting with colleagues or experts if they are uncertain about any aspect of the diagram.

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