What is this physical phenomenon and when it's happen ?
Please take a look at this picture:
Notice: This is a cork ball attracted to sides of a glass of water
Answer
What seems to be happening is that capillary effects in the presence of gravity create a situation in which the cork being maximally decentralized in the glass corresponds to a minimum energy configuration.
My guess is that the cork is non-wetting, and therefore surrounded by a water surface that bends down in the proximity of the cork, thereby creating a minute overall increase of water level in the glass. With the cork resting against the edge of the glass, this water level increase gets minimized.
If all of this is right, the effect should disappear if the cork is replaced by a floating material that is water wet.
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