A ring of mass 4 kg is uniformaly charged with a linear charge density `lambda="4 C cm"^(-1)` and kept on a rough horizontal surface with a friction coefficient of `mu=(pi)/(4)`, A time - varying magnetic field `B=B_(0)t^(2)` is applied in a circular region of radius `(a lt r)` perpendicular to the plane of the ring as shown in the figure. Find out the time when the ring just starts to rotate on the surface . `("take a = 5 cm, g = 10 m s"^(-2) and B_(0)="125 SI units")`

Answer

0.04