How do I find P as a function of r for a Vanderwaals gas?

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SUMMARY

The discussion focuses on deriving pressure (P) as a function of radial distance (r) for a Van der Waals gas, utilizing the equation dP/dr = -rho*g and the Van der Waals equation P = rhot*R*T - a*rho^2. The user successfully applies the quadratic formula to solve for density (rho) and substitutes it into the differential equation. The next step involves separating variables and integrating to isolate P, although the user expresses uncertainty regarding the need for a temperature (T) equation in this context.

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  • Understanding of Van der Waals equation for gases
  • Familiarity with differential equations and integration techniques
  • Knowledge of Archimedes' principle in fluid mechanics
  • Basic grasp of thermodynamic principles, particularly relating to gas laws
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haras
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So, I've been given that archimedes principal for an atmospheric layer of gas on a planet is
dP/dr = -rho*g
where g is constant.

For a vanderwaals gas,
P = rhot*R*T - a*rho^2

I used the quadratic formula & solved for rho and put that into the dP/dr equation. getting...

dP = [((-RT +/- ((RT)^2 - 4aP)^.5) / 2a ] dr

now i need to separate the variables and integrate, to get P as a function of r, but how do i get P out of the right side of the equation?

Thanks!
 
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Don't you need an equation for T?
 

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