I saw a video the other day explaining air pressure where a teacher breaks a ruler by hitting it over a table underneath a sheet of newspaper. I get generally how that works. But then she said atmospheric pressure is 14 psi and so the whole sheet has 7000lb of pressure on it. That’s BS right? Like it clearly doesn’t have 7000 lbs pressed against it? Isn’t that the weight of the column of air above it?
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It does have 7000lbs of force against it, because it has 15 pounds per square inch of pressure on it across 467 square inches, so any one square inch has 15 lbs of pressure. That pressure is the weight of the entire column of air all the way up to space. Air may not be heavy, but once you have a lot of it, it gets heavy. Imagine the newspaper is a suction cup, if you try to pick it straight up off the table, it would take 7000lbs of force to separate it from the table unless you introduce air underneath the suction cup. That air would push up with the 7000lbs of force, because that air would be at the same 15 psi, and the forces balance out, and you only have to overcome gravity to lift the suction cup
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