A175 g ball containing 4.20×10^8 excess electrons is dropped into a 120 m vertical shaft. at the bottom of the shaft, the ball suddenly enters a uniform horizontal 0.200 t magnetic field directed from east to west. part a: if air resistance is negligibly small, find the magnitude of the force that this magnetic field exerts on the ball just as it enters the field.
part b: if air resistance is negligibly small, find the direction of the force that this magnetic field exerts on the ball just as it enters the field. (north, east, south, west)