Q32: Figure P31.31 shows a bar of mass m that can slide without friction on a pair of rails separated by a distance , and located on an inclined plane that makes an angle u with respect to the ground. The resistance of the resistor is R, and a uniform magnetic field of magnitude B is directed downward, perpendicular to the ground, over the entire region through which the bar moves. With what constant speed v does the bar slide along the rails?