A smooth circular track of mass M is vertically hung by a string down the ceiling. Two small rings, each of mass `m`, are initially at rest at the top of the track. They then slide down simultaneously along the track in opposite directions. Find the position of the rings when the tension in the string is zero.
A. `theta=sin^(-1)[(1)/(3)(1+sqrt(1-(GM)/(3m)))]`
B. `theta=cos^(-1)[(5)/(3)(1+sqrt(1-(3M)/(2m)))]`
C. `theta=cos^(-1)[(1)/(3)(1+sqrt(1-(3M)/(2m)))]`
D. `theta=cos^(-1)[(1)/(3)(1+sqrt(1-(5M)/(3m)))]`
