Level pending

A non-conducting ring of Radius R and mass m having charge q uniformly distributed over its circumference is placed on a rough horizontal surface.A vertical time varying uniform magnetic field B= 4t^2 is switched on a time t=0 .The coefficient of friction between the ring and the table , if the ring starts rotating at t=2 sec, is ?

GIVEN; M= 2 kg R = 2 m Q = 2 c g = 10 m/s^2

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