31. Review. Figure P31.31 shows a bar of mass m = 0.200 kg AMT that can slide without friction on a pair of rails sepa- rated by a distance ( = 1.20 m and located on an inclined plane that makes an angle 0 = 25.0 with respect to the ground. The resistance of the resistor is R = 1.00 02 and a uniform magnetic field of magnitude B = 0.500 T 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? B R