Equation p(h): Explained and Derived From Boltzmann's Law

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Discussion Overview

The discussion revolves around the equation p(h) derived from Boltzmann's law, specifically its application in determining pressure at a height h in the atmosphere. Participants explore the equation's components, its derivation, and its relation to hydrostatic equilibrium and gas laws.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant presents the equation p(h) = (p0e)^(-mgh/kT) and questions its name and derivation from Boltzmann’s distribution law.
  • Another participant clarifies that e refers to Euler's number and explains the equation's context regarding pressure at height h and temperature T.
  • A different participant distinguishes between g and G, noting that g is the acceleration due to gravity while G is the gravitational constant.
  • Another participant corrects the placement of p0 in the equation, asserting that it should not be inside the parentheses and emphasizes that the equation is related to hydrostatic equilibrium rather than being a Boltzmann factor.
  • A participant references the Law of Atmospheres, providing a link to additional resources and explaining its predictive capability regarding gas molecules and pressure at height h.
  • One participant adds that m represents the mean molecular mass of air.

Areas of Agreement / Disagreement

The discussion contains multiple competing views regarding the interpretation of the equation and its derivation. Participants correct and refine each other's claims without reaching a consensus on the equation's classification or derivation.

Contextual Notes

There are unresolved aspects regarding the assumptions underlying the equation, the definitions of variables, and the relationship between the hydrostatic equilibrium and statistical physics. The discussion does not clarify these limitations.

yeveat
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p(h) = (p0e)-(mgh/kT)

where p0 is the atmosphere at sea level, m is the mass of an object at height h, g is the gravitational proportionality constant...

is there a specific name for this equation? is this derived from the Boltzmann’s distribution law? Also, I'm really confused about what e is... Thank you!
 
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e is Euler's number, about 2.7. Search wiki for it.

It's the pressure at a height, h at a temperature T. k is Boltzmann's constant.
 
Also g is not the same thing as G. G is the gravitational proportionality constant, g is the acceleration due to gravity.
 
Also,the p_o should not be inside the parentheses. Only the e is being raised to that power. It is not a Boltzmann factor, that would be statistical physics. This is a solution to a force equation, the hydrostatic equilibrium that looks like dp/dh = -rho * g, where rho = mp/kT from the ideal gas law and p is gas pressure.
 
And m is the mean molecular mass of air.
 

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