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Amazing Water Trick

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( 7 comments — Leave a comment )
marmoe
Feb. 19th, 2011 09:31 am (UTC)
 
Needs loooooads of practice. After all, it's a prank to get people flood their kitchen.
marmoe
Feb. 19th, 2011 09:43 am (UTC)
What does work - fill the cup right to the brim, put a card board on top (without leaving any air bubble inside), place it upside down on a desk, lift carefully WITHOUT removing the cardboard. The water will stay inside the cup until the cardboard becomes soggy and tears up. Make a mistake and you are wet. :) Does not work with soapy water, AFAIK.

So, what's happening and why does it not work w/o the card? Air pressure is enough to suspend the weight of the water column. Adhesion of water to the cup and cohesion of the water are strong enough keep the water together as a single bulk. The trouble comes in at the outside surface of the water. The surface tension of the water is not strong enough to keep the surface flat, the surface is unstable. As soon, as the surface bulges out a bit in one place the water column above becomes higher, increasing the pressure in that spot and thus enlarging the bulge - a self-reinforcing circle that makes the water spill out and breaks up the body of the water. The cardboard adds enough stability to the surface to overcome this failure mode.
marmoe
Feb. 19th, 2011 09:44 am (UTC)
 
P.P.S: Very nice CGI in that video. :)
coyoty
Feb. 19th, 2011 11:15 am (UTC)
But you'll notice the water column has the same exact shape and dimensions as the glass, which wasn't full, and there's no splashed water around it when he does the pan-around. The refractions are odd for just water, too.

I'm thinking he did a pan of the glass itself and edited out the flamingos.
marmoe
Feb. 19th, 2011 09:55 am (UTC)
 
P.P.P.S.: This one's not a trick

http://www.youtube.com/watch?v=NJeLqwhIJ9s&feature=related

If you remove the card afterwards, w/o getting an air bubble inside, you may even be able to lift both glasses at once.

Another nice effect: instant ice
http://www.youtube.com/watch?v=DpiUZI_3o8s
You can cool clean, distilled water below freezing. It does not become ice because it's missing a disturbance from where the transition from liquid to ice picks up. Once disturbed - be it by shaking or insertion of an object - that water will freeze. Do not use glassware when trying this out. Water expands on freezing and can break a glass bottle - if you have bad luck, violently.
ccdesan
Feb. 19th, 2011 01:04 pm (UTC)
How many glubglubs do you think will fall for this?
alaskawolf
Feb. 27th, 2011 12:34 pm (UTC)
i can do that outside in winter :)
( 7 comments — Leave a comment )

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