Pulley systems are used in the real world to lift
large masses onto tall heights. You might have seen the workers repairing
the roof of a house and using the pulley system to lift their tools or
materials to the roof. A pulley is an example of a simple machine.
The pulley system consists of one or more pulleys
and a rope or a cable. The number of pulleys used may increase or decrease
the mechanical advantage of the system. Generally, the higher the mechanical
advantage is, the easier it is to lift the object that is being lifted.
Overall, no matter how easy it is to use the pulley
system, the system itself is not very efficient due to the force of friction.
For example, one has to pull two meters of rope of cable through the pulleys
in order to lift an object one meter.
The applet below illustrates just that. Select the number of
pulleys and drag the mouse to see the inefficiency of the system.