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A very pragmatic solution would be to introduce a 3rd camera looking from a 3rd angle to make the problem well-defined. This camera doesn't have to be as good or fast a camera as the other ones (assuming that those are highspeed cameras), because you basically only need 1 frame for which you know for sure which of the 2 possibilities it is. The reason for ...


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Yes, there is some degree of wetting if the angle is <180 degree. Only 180 degree contact angle represents no wetting.


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There are two separate questions here: why do the crumbs clump together? why does the clump form in the centre of the cup? The answer to (1) is discussed in my answer to Why does a cork float to the side of a glass?. Assuming the crumbs are relatively hydrophilic, so the contact angle of water on them is less than $\pi/2$, the curvature of the water ...


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I believe it has something to do with the shape of the glass/cup. Try an irregular-shaped cup or pour milk into a massive massive bowl - try different shapes and sizes and see if the effect is the same. I think in a circular cup there will be force exerted on the milk by the biscuit, but because the glass is round, that force is transferred around the ...


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I suspect the little bubbles are actually CO2. CO2 is water soluble, and you could find it in most forms of tap water. "hard" water tend to have high concentrates of CO2 while softer water have less. If indeed this is the case, the bubbles form because it is energetically efficient to them to adhere to your hand, which is a lower energy state for them. I ...


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For the sake of the explanation I will assume you mean a gas bubble in a liquid*. David Hammen names a few conditions for a bubble to be spherical, in fact you could summarize these all as: for a bubble to be spherical the surface tension has to dominate over other forces (per unit length). If surface tension is indeed dominant than the pressure in the ...


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Rising bubbles of air in a liquid oftentimes are anything but spherical. These bubbles have haphazard shapes because they are rising and because they are interacting with other nearby bubbles. The combination of drag, turbulence, and mutual interactions prevents those bubbles from taking on a nice, simple spherical shape. Here's a rather non-spherical ...


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The thing you'll notice about a sphere is that it's symmetrical. very symmetrical. No matter how you rotate it, it looks the same. the surface tension pulls the surface of the bubble into a shape that has even surface tension over the entire bubble. The shape with even surface tension is a sphere. a sphere has the smallest possible surface area for an ...



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