I noticed this happens when I open the lid of boxes that were in the fridge and accumulated water on their lids.
When I open the lid all of the droplets stay in place but as soon as I flip it vertically they all slide down and drop.
The weight of the droplet is the same, so is gravity, why are the droplets sliding down on the lid rather than staying in place like they were when it was horizontal?
In: 13
The water clings to the lid by *adhesion*: the attraction of the water molecules to the molecules in the lid material. Dripping down requires breaking those bonds, which requires energy.
When the water just slides along, though, it’s breaking and forming bonds at basically the same rate, so there’s no net loss or gain of energy.
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