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motoroller
#2
Oct15-09, 06:13 AM
P: 29
Quote Quote by godzilla5002 View Post
Hello,

I was given a question in school that says use the hydrostatic equilibrium equation and mass conservation equation to come up with a lower limit of the central pressure of a star at it's centre. Here is how I think:

1) Refer to the density in both equations as the same and sub one into the other.
2) After I did I get: dp = -[G*M(r)]/[4*pi*R^4]dm,


Now from here, I want to integrate using dm and M(r),, but M(r) is a equation with respect to r... so I can't right. Is there some insight you can give me to derive a lower limit for the pressure.
Assuming M(r) is independent of r seems to give the right answer but I can't figure out why. That's the only way I can see of doing the problem.