Long enough vertical rails distance L from each other made of an ideal conductor are connected by a resistor R. A bar of mass M, also made of an ideal conductor, can slide along the rails without friction and without loosing electrical contact with the rails. A uniform magnetic field B is horizontal and perpendicular to the plane of the rails. At some point the bar was released with zero initial velocity. Find its velocity after long time. Find the bar's velocity as a function of time (for all times).