A 10.0-cm-long wire is pulled along a U-shaped conducting rail in a perpendicular magnetic field. The total resistance of the wire and rail is 0.350ohms. Pulling the wire at a steady speed of 4.0m/s causes 4.20W of power to be dissipated in the circuit.
part A: How big is the pulling force?
part B: What is the strength of the magnetic field?