A small cork ball A of mass m is suspended by a thread of length I. Another ball B is fixed at a distance I from point of suspension and distance l/2 from thread when is vertical, as shown in figure-1.444. Balls A and B have charges (+ q) each. Ball A is held by an external force such that the thread remains vertical.

When ball A is released from rest, thread deflects through a . maximum angle of `beta = 30^(@)`, calculate m in terms of other parameters