Erica uses a door knob to open a door. A door knob is an example of a wheel and axle. The knob of the door is the wheel and the shaft is the axle. As Erica turns the knob, the shaft is also turned, and the door opens. The knob of a door always has a larger radius than the shaft so that the distance over which the force is applied in order to the effort force needed to open the door. A. Decreases, decrease B. Increases, increase C. Decreases, increase D. Increases, decrease​