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
