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Air - Air pressure - Air pressure and counter-pressure

4 important questions on Air - Air pressure - Air pressure and counter-pressure

What happens if you put two hollow hemispheres together? When do they stick together?

As long as there is air inside of them, they will not stick together. So you still can pull them apart, due to counter-pressure. Soon as you pump the air from between the hemispheres, they stick together, due to the air pressure around the hemispheres.

When do you notice the effects of air pressure?

You only notice them when de air pressure and air-pressure are not equal.

Give an example of the human body that we have counter-pressure?

Our lungs are a hollow space. But we do not feel any pressure in our ribcase. Our ribcase does not collaps either. This comes because our lungs are filled with air. That air exerts counter-pressure that is just as strong als the air pressure outside.

What happens when you have a collapsed lung due to an accident or so?

The air that exerts counter-pressure in that long escapes and you lung turns into a vacuum sack. The air pressure on the outside becomes stronger and your ribcase (can) collaps.