1. Take an empty bottle and a balloon.
2. Insert the balloon into the bottle.
3. Stretch the balloons over the opening of the bottle as shown in the figure.
4. Now try to blow air into the balloon inside the bottle.
5. But it is not easy to blow air when it is inside the bottle.
6. There is some force inside the bottle stopping you to do so.
7. This is because the force applied by the air inside the bottle.
8. The force applied by air on any surface in contact is called “air pressure .
