### Rigid Body

Two identical masses $m$ connected by a massless rod of the length $l$ are moving on a circular orbit $r=\text{const}$ around the Earth. The attraction force between the Earth and a point mass is $|\vec {F}|=GMm/r^2$, where $M$ is the Earth mass and $G$ is a universal constant. Find the frequency of small rotational oscillations of the system (masses on the rod) around the center-of-mass.