The drive element of a pulley system can be a rope, cable,
belt, or chain that runs over the pulley inside the groove.
Pulleys are assembled to form a block and tackle in order
to provide mechanical advantage to apply large forces.
Pulleys are also assembled as part of belt and chain
drives in order to transmit power from one rotating shaft
to another. A wooden pulley of 16.5 cm circumference is
used to transmit power. It has a high co-efficient of
friction.