Understanding Virial Theorem: Comparing Equations

[Stratosphere]

In my astrophysics book, it says it's $$\bar{P}=-\frac{1}{3}\frac{E_{gr}}{V}$$

This Wikipedia article has a different equation. http://en.wikipedia.org/wiki/Virial_theorem

Can someone explain the difference?

 

[sylas]

In my astrophysics book, it says it's $$\bar{P}=-\frac{1}{3}\frac{E_{gr}}{V}$$

This Wikipedia article has a different equation. http://en.wikipedia.org/wiki/Virial_theorem

Can someone explain the difference?

Yes; the variables being used are different. Your formula is using pressure and volume. Wikipedia is using kinetic and potential energy, and the "virial". Should work out to be the same, I think.

Cheers -- sylas