The Physics of Liquid Droplets

According to Physics textbooks (and practical experience), if I want to slide a box across the floor, I will have to apply more force in order to get a heavier box to move than that required to slide a lighter box across the same floor. A team of scientists at Lamar University in Beaumont, Texas, however, published a report, in the 25 December 2009 issue of Physical Review Letters, on a seemingly similar situation, where this same concept does not apply. They measured the force required to push a millimeter-sized droplet across a solid surface and found that a droplet hanging upside-down from the surface needed more force to get moving than a droplet resting its weight on top of the surface. One theory for this is that the differences in molecular orientation between "hanging" and "resting" droplets may change chemical interactions between the solid surface and the liquid. All I know is that this Blind Bambi is glad that there are people much smarter than I to figure things like this out.