What is meant by pressure being a momentum flux?

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    Flux Momentum Pressure
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Discussion Overview

The discussion revolves around the concept of pressure being described as a momentum flux, particularly in the context of an equation of state. Participants seek to understand the physical meaning of this characterization and the implications of the associated equation.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant inquires about the physical meaning of pressure as a momentum flux and requests clarification on the equation provided.
  • Another participant explains that a flux has units of something per area per time, suggesting that momentum flux can be expressed in terms of its basic units.
  • A different participant connects pressure to force density and momentum transfer rate, indicating that pressure can be interpreted as momentum per time per area.
  • One participant challenges the consistency of units in the equation presented, proposing that "volume" should actually be "velocity" and suggesting a misinterpretation of the original equation.

Areas of Agreement / Disagreement

Participants express uncertainty regarding the interpretation of the equation and the consistency of its units. There is no consensus on the correct interpretation or the validity of the equation as presented.

Contextual Notes

Participants note potential issues with unit consistency in the equation and the interpretation of terms such as "number density" and "momentum." There are unresolved assumptions regarding the definitions and context of the terms used.

Who May Find This Useful

This discussion may be useful for those interested in the physical interpretation of pressure in fluid dynamics, momentum transfer, and the mathematical relationships in equations of state.

clumps tim
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hi, I have been working on equation of state and one of my article says pressure is a momentum flux. what is the physical meaning of this? they have written it as

pressure =(1/3) *number density*volume*momentum

please explain me the expression

regards
 
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I'm sorry you are not generating any responses at the moment. Is there any additional information you can share with us? Any new findings?
 
no not yet, how is pressure a momentum flux?
 
A flux of something has units of something per m2 per second: something / (m2·s).

So momentum flux would be (kg·m/s) / (m2·s). I'll let you simplify it.

Pressure is force per unit area: N/m2. Expand the Newtons into basic units, simplify, and compare with the units of momentum flux.
 
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clumps tim said:
no not yet, how is pressure a momentum flux?

force is a momentum transfer rate:
momentum / time

pressure is force density :
force / area
or:
momentum / time / area
 
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clumps tim said:
pressure =(1/3) *number density*volume*momentum

Assuming that "number density" means something like "molecules per m3" and "momentum" means "momentum per molecule", the units are not consistent in this equation. I think "volume" should be "velocity", i.e. you have mis-interpreted a "v" in the original equation.
 
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thank u all.
 

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