1. Dec 1, 2009

### Unto

Sorry noone was answering my question, and I just wanted to get this done:

1. The problem statement, all variables and given/known data
...Hence show that the mass of the star is M = $$4\pi$$$$p_{c}$$$$\left(R^{3}/3 )$$

2. Relevant equations
M(r) = $$4 \pi$$$$p_{c}$$$$\left(r^{3}/3 - r^{4}/4R)$$
This is the mass within a radius

3. The attempt at a solution
I already found the mass within a radius via intergration (look at relevant equations), and I know that I have to build up an 'infinite' number of radial masses to get the whole mass of the star. But do I use integration on this equation or something else? What do I do?

2. Dec 1, 2009

### Unto

Oohh for f_cks sake.... I realised

Total radius of the star is 'R'. Just substitute that in for $$r$$ and cancel, since r1 is subjective and doesn't factor for the whole star.

WHHHYYYYYY!??

3. Dec 2, 2009

### Matterwave

The total mass of anything is just M=pV where p is the average density and V is the volume. Here V=4/3*pi*R^3. That's that...