In 'nearly' circular motion, the radius is not constant. If the force is central the and the angular momentum is still conserved, we have a central force:
where $r_0$ is equilibrium position.
For this motion, the orbital radius will 'oscillate' due to the centripetal and centrifugal force. However, in such motion, I am not sure how the angular frequency is given by:
whereby $Ω$ is the angular frequency due to the 'oscillating' radius, and ω is the angular frequency of the orbit itself.
Any help in explaining this concept and explaining how the angular frequency is derived will be appreciated.