Pulleys

Learning objectives

To compare the properties of fixed pulleys and pulley systems.
To illustrate the usefulness of pulley systems.
To address the notion of energy in order to teach that it is conserved.
To introduce other devices that can be used to multiply forces (levers, pedals, wheels).

This animation enables you to compare the properties of a fixed pulley with those of a pulley system. One pulley enables you to change the direction in which a force acts. Associated with one or several other pulleys (compound devices) the pulley enables one to reduce the force needed to lift a mass.

Note that the distance the mass is displaced is reduced by a factor identical to the factor of reduction of the force. Thus, for a system with two pulleys, the force needed is halved, but the so is the height of displacement. Energy is thus conserved.

Note: The friction and weight of the cord and the fasteners is ignored.