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Question:
why are we not crushed by air that is as heavy as a volkswagon?



Replies:
Air is pretty light actually, about 1000 times lighter than water or milk. That is why a one-gallon milk container is so light when the milk is poured out (although there is air in it).

I suspect that your question is about air PRESSURE. The air around us is pressured (called atmospheric pressure) and you can see its force by a simple experiment in which a small amount of water is boiled inside a can of coke and then the can turned upside down into a tank of water. As the water vapor that has displaced the air in the can is condensed (turned into water), the pressure inside the can drops. But the pressure outside the can is still atmospheric pressure. This excess external force crushes the can. Why doesn't air pressure crush us? The pressure inside our body is roughly the same as the pressure outside and therefore there is no net pressure (and thus, force) on us.

But what if we go to an environment with higher or lower pressure? The magnitude of air pressure around us is like that of a 10-m-tall column of water. If a diver goes 10 m under water, the pressure on his body is doubled but this still will not crush him because much of his body is composed of liquid (and not gas) and cannot be compressed (shrunk). Human organs or areas filled with air, such as middle ear or the lung, however will be pressurized (squeezed) as one dives deeper and expands as one comes to the surface. Proper training and slow descent and ascent are necessary to make sure the air inside the body does not expand or contact too rapidly causing injury.

You can experience the force exerted by pressure differences by noting that the volume of an air-filled balloon will shrink by as it is pushed under water. The pressure outside due to atmosphere and water is higher than inside and this lead to the shrinkage.
Good luck.

Dr. Ali Khounsary


This is a very good question. It is because the air is a fluid. It flows around us and into us. From inside us (in our lungs) it exerts the same force as it exerts from outside. The result is the force of the external air trying to 'crush' us is exactly equal to the force of the internal air trying to 'explode' us.

Bradburn



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