Lesson 4 of 8
Atmospheric pressure
Goal: Explain atmospheric pressure and why it falls with height.
The air above you has weight. It presses on everything below it. This is atmospheric pressure.
- At sea level it is big: about 100 000 N on every square metre. It pushes on you from all directions. It does not crush you, because the pressure inside your body pushes out just as hard.
- Higher up, it is lower. There is less air above you, so less weight presses down.
- The air is thinner too. High up, the particles of air are further apart. Fewer of them hit you each second, and each breath holds less oxygen. That is why climbers on the highest mountains carry oxygen.
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Key words in this lesson
Pressure The force on each unit of area
Atmospheric pressure The push of the air, caused by the weight of the air above