From times immemorial, man has used machines to help him in his work. Today, we are dependent on machine for almost every task. When we think of machines we always tend to think of big and complicated units with many moving parts like wheels and rollers and gears and shafts. In Physics the term 'machine' has a specific meaning.
It is a device which helps us to do the work at one point and deliver at another point with a view of accomplishing the work more easily or with a gain in speed.
A single pulley changes the direction of applied force.
In order to change the tyre of a car, we use a jack to raise the car. In a garage, for the repair, engine of an automobile is lifted up with the help of a system of pulleys.
