Ch - Simple Machines

What Are Machines ? 

There are many tasks that we cannot do ourselves, or we may need to put in a lot of time and effort to do them. To do such tasks, we use machines.
  • A machine in the broad sense of the word is any device designed to translate some form of energy into useful work.

Why we need Machines ? 

  •  A machine is a tool that makes our work easier
  • . It helps us to overcome a larger force (required to move a load) by applying a lesser force (called effort).
  •  Machines can be simple or complex. 

What are Simple Machines ? How simple machines are useful ? 



A simple machine uses a single applied force to get the work done.
  •  A “simple” machine is one where both the input energy and the output energy are mechanical in nature .
  •  A simple machine has very few parts. 
  • A wheelbarrow is an example of a simple machine

Different Types of Simple Machines 

There are mainly 6 types of simple machines.
  1. Pulley
  2. Wheel and axle
  3. Lever
  4. Wedge
  5. Screw
  6. Inclined plane

What is Lever? 



A lever is a simple machine consisting of a rigid rod which is capable of turning around a pivot called a fulcrum.
 It has three parts, namely, effort, load and fulcrum.
  • Fulcrum: The point on which the lever turns or balances. The rod of the lever rests on it and the lever rotates on it.
  • Load: The weight lifted by the lever is called the load.
  • Effort: The force applied on the other end of the rod to lift the load is called the Effort.

Types Of Lever 

  1. First class Lever / Class one Lever (Load -Fulcrum – Effort )
  2. Second Class Lever/ Class two Lever(Fulcrum – load– Effort )
  3. Third Class Lever/ Class Three Lever (Fulcrum – Effort – Load )

What is Pulley ? 



A pulley is a wheel that carries a flexible rope, cord, cable, chain, or belt on its rim. The pulley is designed to support   movement and change the direction of the cable.

Simple Pulley 

 A pulley is a simple machine used to lift heavy objects.
  •  A pulley consists of a wheel with a grooved rim and a rope, chain, or belt wound around it.
  •  The wheel rotates around an axle. 
Example: The Garage door is an example of pulley

Types Of Pulleys

Pulleys are of the following two types:

 Fixed pulley

  •  This type of a pulley has a fixed axle.
  •  A fixed pulley makes work easier by changing the direction of the force.
  •  This type of pulley is used to draw a bucket of water from a well. 

Movable pulley 


  • This type of a pulley has a free or movable axle.
  •  It is used along with a fixed pulley.
  •  For example, a crane uses both fixed and movable pulleys to lift heavy loads.

Activity to demonstrate Working of Pulley

Aim To demonstrate the working of  pulley. 

Materials: A half-meter long, strong thread, a spool of pulley of a thread, a long pencil, a heavy bangle, a table, and many small books. 

Procedure:
  1. Pass the pencil through the spool. 
  2. Make two stacks of books. (Keep them apart on the table).
  3.  One end of the pencil should be kept on each stack of the books. [Note: The pencil with the spool should be at least two feet above the table],
  4. Pass the thread over the rim of the spool. Tie one end of the thread to the bangle.
  5. Now pull the other end of the thread.
Observation: The bangle is lifted up on pulling the other end of the thread. 

Conclusion: The spool acts like a pulley. It is a simple machine that helps to lift heavy objects. 

What are Wheel And Axle? 


A wheel and axle is a simple machine made up of a wheel rigidly attached to a  rod (called an axle).
When one rotates the wheel, the axle also rotates. 

Example Of Wheel And Axle

 A steering wheel and a doorknob are examples of wheel and axle. 

What is an Inclined Plane  ?             

  • An inclined plane is a tilted surface or a slope 
  • An inclined plane is  used to move a heavy load with less effort
Example: Ramps in hospitals and slides on the playground are examples of inclined planes. 

What is a Screw ? 

The head of a screw is twisted, spinning the threads and causing the screw to move forward
  • It is a kind of simple machine in which nail with grooves cut on it.
  •  A screw is a modified inclined plane
  • It has a groove at its head into which the tip of a screwdriver fits easily.
  •  It is used to hold things tightly together. Screws are used in objects such as light bulbs.
  •  It has a thread, that is a winding edge and which is an inclined plane wrapped around the screw.
  • With the help of a screwdriver it is easy to drive screws into wooden blocks.
  • A Screw jack is a big screw which  works on the principle of screw and it is used to lift cars , trucks etc.
Example: The bottle caps are examples of screw. 

What is Wedge? 


  •  A wedge is a simple machine that has a long triangular shape with one broad or blunt end, and one sharp end. 
  • The sharp end is used to cut or slice objects.
  •  A wedge may also be formed when two inclined planes are joined together.
Examples: The head of an axe and the blade of a knife are examples of a wedge. 

Activity Demonstrate the Working of Wedge

Aim: To demonstrate the working of a wedge. 

Materials: A knife, an apple, a pencil, and a plate

Procedure: 
  • 1. Place the apple on the plate
  • 2. Try to cut it into two halves with the help of the pencil.
  • 3. Next try to cut it into two halves with a knife. 
Observation: It is not possible to cut the apple with the pencil. But it is easily cut with the knife.

 Conclusion: Knife is a simple machine.