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I was learning about fluids and I randomly thought of suction cups. I think they're a really cool application of air pressure. When you squeeze the air out, the outside air pressure exerts a huge force on the cup, meaning it will hold in place.

However, I was thinking about how I could actually squeeze out the air in the first place, given that the pressure of air is $101kPa$. At first I was horrified - my little arms can't dish out 100,000N! But then I realised that the average suction cup is only a few $cm^2$ so if you multiply the pressure by the total area, it is actually quite a small force so it's quite manageable. However, if I did have a suction cup measuring 1m by 1m, then wouldn't it be impossible for me to be able to exert 100,000N to actually remove the air in the first place?

Does this mean that there is a limit on the size of suction cups because otherwise humans are not able to actually squeeze out the air from them?

John Hon
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1 Answers1

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I don't think the air pressure matters - that's always present. By your logic as stated, you couldn't push all the air out of an air mattress either. All that matters is the resistance of the suction cup material itself, as that is what you're deforming.

Carl Witthoft
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