The main difference between airplane and automobile wheels is that airplane wheels have to be able to rotate in both directions, while automobile wheels only rotate in one direction. This is because the main force acting on an airplane wheel is the drag force created by the air as the plane moves through it. Since the direction of this drag force changes as the plane moves through the air, the wheels need to be able to rotate so that they always face in the correct direction. Automobile wheels don't need to rotate in both directions because the only...