What is Energy?

Energy is the ability to do work

Work can be done only if a body has energy

Example

Suppose we want to kick a football

Kicking a football is 'work'

To do this work, our body should have energy

When we kick a football, energy gets transferred from our body to foot ball

This makes football move

Important Points about Energy

An object must have energy

This energy can exert force on other object

When work is performed, energy gets transferred from one object to another object

Example

To push a heavy box, we must posess energy

This energy of our body exerts force on the box

When work is performed on moving the box, muscular energy of our body gets transferred to kinetic energy of the box

This makes the box move

What is SI Unit of Energy

Energy is measured in Joule (denoted by J)

Note

SI unit of Work and Energy are Same

Both are measured in Joule (denoted by J)

This is because Energy required to do 1 Joule of Work is called 1 Joule Energy

Sometimes, energy is also measured in Kilojoules

1 Kilojoule = 1000 Joules

or

1 kJ = 1000 J

How to calculate amount of energy posessed by body?`

It is equal to amount of work body can do when energy is released