Water Dops

[morkris]

do water drops roll or slide down glass

[lisaj]

I think they roll, and this would be far easier to explain with a diagram (I'm also away that 'meniscus' is not precisely the correct word to use :-): The suface tension of the water initially forms a meniscus with the surface of the glass. The weight of the drop would begin to droop down. As it did so, the drop's surface tension would make the top part of that meniscus pull away from the glass, whilst the lower, fatter edge would be pushed against it, extending the lower part of the meniscus. As this continues, tiny parts of the drop are left behind on the glass, so its size diminishes as it goes down, and ultimately you get either no drop, or a small drop whose weight is insufficient to break the surface tension's grip with the glass.

[morkris]

Thanks Lis. Confirmed my thoughts ! strange how these things come to mind in the shower