Yep inertia and centrifugal forces are intriguing really. I once worked on robotic assembly line machines where tiny little parts dumped from a box of 10000 into a dish like hopper would travel up a narrowing spiraling ramp until they reached their point of individual use. They "magically" lined up like little soldiers. So it was vibration that caused the travel. The spinning thumper underneath this spiral ramp had to rotate the opposite direction of the ramp. Otherwise they would never leave the dish. Go figure.