How do suction cups work to hold things up?
In: Physics
The atmosphere is held down by gravity. Because gravity exerts a downward force on every atom of the atmosphere, the atoms down by the ground are under a lot of weight from the atoms above. This gives our atmosphere air pressure.
When there is a difference in pressure, the universe will try to equalize the difference. This causes high-pressure air to move to lower-pressure areas. If the air can’t move though, a static force is generated as the pressure tries, but fails, to move the air. We can take advantage of this force by placing a membrane (the suction cup) between the area of high and low pressure.
By pushing the suction cup against a flat surface, you squeeze most of the air out, leaving an area of low pressure between the surface and your suction cup. Since this suction cup exists in earth’s atmosphere, the surrounding air has a higher pressure. The higher pressure wants to move to the lower pressure area, but it can’t, because the suction cup creates a seal. The air never stops trying though, as long as the difference in pressure exists, the air will try to move through the suction cup. This attempt to move generates a force on the suction cup. That force presses the suction cup into the surface.
TLDR: Suction cups redirect gravity using the atmosphere.
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