# Finding the density of the matter

1. Jan 30, 2010

### dingo_d

1. The problem statement, all variables and given/known data

Find the density of the matter $$\rho(\vec{r})$$ in spherical coordinate system, with the mass M, which is homogeneously placed on two rings with the radii of a (with the center in the origin) put in the xy and yz plane

2. Relevant equations
$$\int \rho(\vec{r})dV=M$$
For a unit mass in the center that would be:
$$\int dx\int dy\int dz M\delta(x)\delta(y)\delta(z)=M\cdot 1\cdot 1\cdot 1$$
in cylindrical coordinates:
$$\rho(\vec{r})=\frac{M}{2\pi \rho}\delta(\rho)\delta(z)$$
$$\int\rho(\vec{r})dV=\int_{-\infty}^\infty dz\int_0^{2\pi}d\phi\int_0^\infty \rho d\rho \cdot\frac{A}{2\pi\rho}\cdot\delta(\rho)\delta(z)=M\Rightarrow M=A$$

3. The attempt at a solution

I don't know even how to start :( Help plz...