# Help! Conservation Of Mass

1. Mar 20, 2005

### GotTrips

Hi all
I am in deperate, desperate, desperate need of some help. I have this question that I have been working on for hours and have made no progress at all.

Here is the question.

Write down the "conservation of mass" equation for dm(r)/dr, where m(r) is the mass inside radius "r". Assume that the pressure inside a star at radius r is given by

P(r) = Pc/R(R-r)

where Pc is the central pressure and R is the stars outer radius. Combine this and the equation of hydrostatic equlibrium to find an expression for m(r). Hence show that m(r) x r5/2