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Machines - I


Machines have been used for centuries not only to make work easy, but also to make it efficient and safe. As the name suggests, the constructions of simple machines are not complicated and they are used for day-to-day simple works. The other characteristic feature of simple machines is that they do not convert energy from one form to another. Complicated machines such as bicycles and screwing machines are made up by combining two or more simple machines.

Simple machines can be broadly classified into two categories.

  • Lever
  • Inclined plane

These two types are further divided into sub-categories, as shown in the given diagram.


  • A lever is a rod which moves freely about a fixed point called the fulcrum. 


  • An inclined plane provides a sloping surface over which heavy things can easily be lifted or rolled down.

There are certain common terms that are used for almost every simple machine. Let us understand these terminologies first.

Machine Terminology

  • Effort — The force applied to a machine to do mechanical work is called effort.
  • Load — The force applied on an object by the machine is called load. When a crow bar is used for lifting an object, the weight of the object is the load, as that is the amount of force the simple machine has to apply to lift the object.
  • Fulcrum — When a machine does mechanical work by turning on a point, the point of rotation is called the fulcrum. In the given picture, the middle point is the fulcrum of the seesaw.

  • Input Energy — The work done on a machine or the energy supplied to a machine is called input energy.
  • Output Energy — It is the work done by the machine or the energy obtained from the machine.
  • Principle of Machine — In an ideal machine, the output energy is equal to the input energy. Therefore, mathematically we can express it as. This is called the principle of machine.
  • Mechanical Advantage— It is the ratio of the force obtained from the machine to that applied to the machine. In simple words, we can say
  • Efficiency — The ratio of the energy obtained from the machine to that supplied to it is known as the efficiency of the machine. It is obtained by dividing the am…

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