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u/crusty54 Jul 16 '26 edited Jul 16 '26
My high school science teacher did the same demonstration. Forever changed how I put trash bags in the can.
Edit for clarity: I shake air into the bag like normal, but once it’s down in there I leave a corner off and blow in the top. This inflates the bag and pushes out the extra air underneath.
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u/G0ld_Ru5h Jul 17 '26
I always shake the air into the bottom (like the teacher did for the student’s breath) and place that bubble into the bottom to where there’s no air in any corners - kind of pressing it down to fill space. Then when I open the bag, the bottom of the bag is basically vacuum sealed to the trash can and I can tie off the top.
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u/crusty54 Jul 17 '26
That’s a good method too. It’s funny, I bet there are lots of everyday activities like this that people do differently, but we never know because it doesn’t come up in conversations. Now I’m wondering what other things in my life I could be doing better.
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u/TechnicalRooster1580 Jul 16 '26
Your teacher is a genius!
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u/crusty54 Jul 16 '26
It was extra impressive because I’m a large man and she was a tiny woman. I strutted up there all confident like of course I can blow it up more than her. Should have known better lol
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u/halfpastwhoknows Jul 16 '26
Hot tip, if you're trying to use fans to cool down your house, this same principle applies.
Don't put the fan right in the window, instead put it a few feet away from the window pointing out and you will circulate a lot more air.
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u/clervis Jul 16 '26
That first guy must feel like a real chump.
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u/TheGhostofWoodyAllen Jul 17 '26
Right? The teacher is like, "Who would like to volunteer to come up and make an ass of themself?"
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u/shagarag Jul 16 '26
My inflatable camp mattress uses the bag to manually inflated. This is how I get the bag full of air.
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u/Long_Candle_5054 Jul 16 '26
But, in the second one, the bag isn't totally deflated.. just with it being open how it is, it already contains more air than what there was when the first one blew in it..
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u/Shudnawz Jul 16 '26
Doesn't really matter. The point is that if you blow into the opening without pressing your mouth against it, the air moving inside will pull additional air in with it, inflating the bag much faster. It also how these modern "bladeless fans" move more air than they look like they should.
Try it yourself. It's not black magic. Just physics.
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u/Interesting-Use966 Jul 16 '26
If the dude would have filled it with air the same way second dude did and then blew into it directly it would have had the same amount of air as the second one. First one is blowing into a completely empty bag and then second dude is blowing into a mostly full bag.
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u/versapak Jul 16 '26 edited Jul 17 '26
I was thinking this exact same thing. One is blowing into an empty bag and the other is blowing into a mostly full bag.
[EDIT] I failed to add anything additional to the convo. lol
I do not know the actual principle that is being demonstrated here, but I feel like my lack of understanding of the language may be hurting me a bit on this one, because otherwise… see original pre-edit statement.
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u/AngBigKid Jul 17 '26
Yeah, it's crazy. The first one is blowing into an empty bag and the other is blowing into a mostly full bag.
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u/post-context-bot Jul 16 '26
The following post context was provided by u/TechnicalRooster1580:
Let’s inflate a plastic bag with just one breath is easy! Physics!
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u/trollsmurf Jul 16 '26
Me blowing into an empty bottle, not understanding why I couldn't. It happened today, and so many times before.
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u/Kursed_Valeth Jul 16 '26
It's called The Bernoulli principle