#Physics / #mechanics #puzzle.
In the picture below, a blue ceramic 500ml bowl weighing 330g has a white silicone cover on it. A hand holds the bowl+cover in mid air.
The cover was just placed lightly on the bowl before it was picked up.
What is holding the bowl up?
(I have my own ideas that I'll put in a reply tomorrow)
Discussion
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@bigblen
The bowl contained hot steam. The steam blows out around the lid, but then when it cools, the lid is pushed down by air pressure which, with the moisture, forms a seal around the rim. The vacuum inside is strong enough to seal the lid on and hold the bowl up.
@bigblen Ooh ooh I know this one: the hand is holding it up!
Also I'm presuming air pressure differentials hold the silicon cover to the rim of the bowl with a greater force than gravity pulls the bowl to the floor.
There was no hot steam in the bowl, the lid is easily removed by lifting the edge.
I find this thing interesting because air seems so insubstantial, yet it is pushing the bowl upwards.
To lift the bowl, about 3.2N force is required. The area of the bowl bottom is about 0.03m². Combine these to get 100Pa net upward pressure.
Atmosphere pressure is about 100kPa (equivalent to 1kg/cm² or 15psi) - about 1000x more!
1/2
Boyle's law says Pressure x Volume = Constant. To decrease pressure by 1/1000, increase volume by 1/1000 (approx). So the lid only needs to bulge up by about 0.5ml to create enough pressure difference "vacuum" to lift the bowl up.
2/2
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