Hydrostatic Pressure: Liquids or Air?

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Discussion Overview

The discussion revolves around the applicability of the hydrostatic pressure equation to both liquids and gases, particularly focusing on whether the equation can be used for air pressure in addition to liquid pressure. Participants explore theoretical implications, practical applications, and experimental observations related to hydrostatic pressure.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Experimental/applied

Main Points Raised

  • Some participants assert that hydrostatic pressure applies to both liquids and gases, citing atmospheric pressure changes with elevation as analogous to liquid pressure changes with depth.
  • One participant provides the hydrostatic pressure equation, p = p0 + (rho)gh, and questions its applicability for calculating pressures at different elevations in both oceans and mountains.
  • It is noted that using the hydrostatic pressure equation for air may be problematic due to the compressibility of gases, unlike incompressible liquids like water.
  • A participant shares an experimental observation that the pressure at the top of a water-filled container appeared greater than at the bottom, prompting questions about the validity of the hydrostatic pressure equation in this context.

Areas of Agreement / Disagreement

Participants express differing views on the applicability of the hydrostatic pressure equation to gases, with some supporting its use and others highlighting limitations due to gas compressibility. The experimental observation raises further questions, indicating that the discussion remains unresolved.

Contextual Notes

Limitations include the assumption of constant density in the hydrostatic pressure equation, which is valid for liquids but not for gases. The discussion also reflects uncertainty regarding the interpretation of experimental results related to pressure measurements.

MyNewPony
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Is the equation for hydrostatic pressure limited to liquids? Or can it be used for air pressure as well?
 
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The concept of 'hydrostatic pressure' applies to fluids, either liquid or gas. Remember the pressure of the atmosphere decreases with increasing elevation, or increases with decreasing elevation, just as pressure in the oceans increases with depth.

Please provide the equation to which one is referring.
 
Astronuc said:
The concept of 'hydrostatic pressure' applies to fluids, either liquid or gas. Remember the pressure of the atmosphere decreases with increasing elevation, or increases with decreasing elevation, just as pressure in the oceans increases with depth.

Please provide the equation to which one is referring.

Sorry, here it is:

p = p0 + (rho)gh

So, I can calculate both the pressure at the bottom of an ocean and the pressure at the top of a mountain using this method?
 
MyNewPony said:
Sorry, here it is:

p = p0 + (rho)gh

So, I can calculate both the pressure at the bottom of an ocean and the pressure at the top of a mountain using this method?

In the case where the density does not change with pressure. For water (an incompressible fluid), that's a good approximation. For air, that's a bad approximation.
 
MyNewPony said:
So, I can calculate both the pressure at the bottom of an ocean and the pressure at the top of a mountain using this method?

If you can get the exact density of the air on that heigth.
 
i just wondering..i conduct an experiment last week on pressure inside a container.note that the container is filled with water.i've found out that the pressure on the top of the container is greater compared to the lower of the container.it's suppose to be the opposite right based on P=pgh?why does the this occurred and please correct me if I'm wrong.i used the pressure gage to take the measurement.
 

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