Below the fixed end O of the insulating horizontal thread OB, there is a fixed charge A of `Q = 20muc`. At the end B of the thread there is a small mass m carrying charge `Q = 20moc`. The mass is released from the position shown and it is found to come to rest when the thread becomes vertical. Assume that the thread does not hit the fixed charge at A. `[g = 10 m//s^2]` (a) Find mass m. (b) Find tension in the thread in the equilibrium position when the thread is vertical. (c) Is the equilibrium mentioned in (b) stable or unstable?

Answer

(a). 72g
(b). 4.32N
(c) unstable