Ok there are two plastic rails over which a metal wire is kept , the wire is kept prependicular to both plastic rails , over the rails.. The coefficient of friction is 'n' between the metal and the plastic . The mass of the plastic wire is 'm' , Calculate the magnitude of the Magnetic field B , which just allows the wire to move. I equate dthe net frictional force which will try to limit the motion , with the Magnetic force given by ILB , but in the answer instead of 'n' . there is some square root fuction of 'n'in the denominator and n in the numerator. , please help.