## What is Pendulum?

It is a body which hangs from fixed point

It swings back and forth (move form left to right and right to left)

## How is simple pendulum made

It contains a heavy metal ball which is tied to a string

This string is attached to a support such that metal ball hangs down

## What is Conservation of Energy

When energy changes form from one form to other

Total Energy remains constant

There is no loss or gain of energy

## How does Pendulum work on Principal of Law of Conservation of Energy ### When the ball of Pendulum is pulled to one side and not yet released

It has Potential Energy but not Kinetic Energy

(Suppose Potential Energy is 10 J, Kinetic Energy = 0 Joules = Total 10 Joules)

### When ball is released from hand,the ball loses potential energy and gains kinetic energy

(Suppose Potential Energy decreases to 8 joules, Kinetic Energy becomes 2 joules, Total = 10 Joules)

When it reaches center position

It has only kinetic energy but no potential energy

(Suppose Potential Energy = 0J, Kinetic Energy = 10J, Total Energy = 10J)

This kinetic Energy makes the metal ball move towards other side

As it moves uPwards towards other side, kinetic energy decreases and potential energy increases

(Suppose Potential Energy = 2, Kinetic Energy = 8J, Total Energy = 10J)

It soon reaches a point where potential energy becomes maximum and kinetic enrgy becomes 0

(Suppose Potential Energy = 10J, Kinetic Energy = 0 J, Total Energy = 10J)

Hence, Total Energy in all cases remain constant at 10 Joules

## Questions

NCERT Question 15 - Illustrate the law of conservation of energy by discussing the energy changes which occur when we draw a pendulum bob to one side and allow it to oscillate. Why does the bob eventually come to rest? What happens to its energy eventually? Is it a violation of the law of conservation of energy?

1. Class 9
2. Chapter 11 Class 9 - Work and Energy (Term 2)
3. Concepts 