5) Bonus: Suppose a conduction rod (mass m, resistance R) rests on two frictionless and resistanceless parallel rails a distance / apart in a uniform magnetic field is ( 4 to the rails and to the rod). At 1=0, the rod is at rest and a source of emt is connected to the points a and b. Determine the speed of the rod as a function of time if the source puts out a constant current I. O O O B O O O O O O b O O O O O