A nonconducting ring of mass m and radius R, with charge per unit length `lambda` is shown in fig. It is then placed on a rough nonconducting horizontal plane. At time t=0, a uniform electric field `vecE =E_(0)hati` is switched on and the ring starts rolling without sliding. Determine the friction force (magnitude and direction ) acting on the ring.

Answer

`lamdaRE_0 hati`