Magnetic Field

A metal wire of mass m slides without friction on two horizontal rails spaced a distance d apart, as shown in Fig. 32-36 below. The track lies in a vertical uniform magnetic field B. A constant current i flows from the generator G along one rail, across the wire, and back down the other rail. Find the velocity (speed and direction) of the wire as a function of time, assuming it to be at rest at t=0.