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Comment by d--b

2 years ago

I guess this is somewhat counter intuitive:

https://www.youtube.com/watch?v=NBsvzMi9-f8

So yeah, fans are puzzling too.

2 comments

d--b

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convivialdingo  2 years ago

If you watch it very slowly, the paper initially folds under the mouth and then it blows out straight.

I'm guessing the initial puff creates a high pressure area on top of the paper, rolling it downward and back. Them after the puff has pushed the air away, there is now a low pressure zone on top of the paper which lifts it up as the air below is rushing upwards around the sides of the paper.