Circular Horizontal Motion of a Ring Threading an Inelastic String

If a ring of mass m is threaded on a string of lengthtied to points A and B with B vertically below A and l >AB the ring can be made to execute circular horizontal motion.

Resolving vertically for the ring gives (1)

Usinghorizontally gives (2)

gives

Hence (3)

Simple trigonometry givesandand since the length of the string is

Substitute this into (3) to obtain