Why does the wet plate move? Sometimes when i put a wet plate on a flat-solid-slick surface the plate will begin to move after some slight initial rest.  what law(s) of physics explains this rare phenomena? is it just hydroplaning?
 A: if you place the plate on a wet surface, you trap a cushion of air under it. the water under the plate begins to evaporate into the trapped air, increasing its volume slightly. The expansion lifts the plate just out of solid contact with the countertop but leaves a continuous ring of water all the way around the plate rim, preventing the expanding air from escaping. now the plate is floating almost frictionlessly on the trapped bubble of air and the slightest perturbation will cause the plate to slide sideways.
This principle is used to gently move huge pieces of machinery. Here you place a huge soft rubber cup under the machine and blow air into the space between the cup and the floor. the machine lifts up just until air starts to hiss out the gap between the lip of the cup and the floor, at which time you can push on the machine with your hand and set it to slide like a hockey puck even though it weighs several tons. As long as you keep pumping air into that space, the machine will continue to float on that air cushion and you can easily move it anywhere you want on the floor- even up a ramp and into a truck or onto a fork lift platform.
