hello I am confusing about a physics problem right now. instead of gravity, two planets are connected by a spring with spring constant K. And since the mass of one planet is much bigger than that of the other. So, lighter planet does circular motion around the heavier planet. Then, it asks ω (angular velocity) of this circular motion (no gravity between these two objects). I know that the equation for this problem is that mv^2/R=kx (centripetal force is supplied by the spring) but, my TA said that x=R in equilibrium position. And the ω=(k/m)^(0.5) I don't understand it ! Thank you very much if you can clarify this point !