Science · 6 pages · 12 min
How atmospheric pressure holds a suction cup
The cup stays up because the air outside pushes harder than the air underneath.
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From the opening
Atmospheric pressure holds a suction cup because pressing it flat pushes most of the air out and the soft rim then seals. Outside air pushes on the cup with the full pressure of the room, while the thin air left inside pushes back with less. The opening covers less pressure under the cup, why the rim has to seal, and the limit set by air pressure.
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Inside
- Less pressure under the cup
- Why the rim has to seal
- The limit set by air pressure
- Magdeburg hemispheres as a large cup
- Where the idea stops applying
- A distinction worth keeping
Sources
- Holding force as pressure difference times area
- The Magdeburg hemispheres and the weight of the atmosphere