A rubber cleaning pad is held stationary against the right-hand face of a vertical moving belt. The belt moves vertically upwards past the pad.
Describe the directions of the friction force and the normal contact force exerted by the belt on the pad.
The belt is then made to move vertically downwards. The pad remains against the same face of the belt.
Explain how the direction of each force exerted by the belt on the pad changes, if at all.