An interesting variation on the Pitch Drop Experiment http://www.physics.uq.edu.au/physics_museum/pitchdrop.shtml might be a sealed barrel or jug half-full of pitch rolling down a gentle incline. I'm trying a similar experiment with bottles of "gel-caps" (or "soft-gels") of oil-soluble vitamins (e.g., E, A, or lycopene) which adhere when left undisturbed, but gradually separate under very light force, making little clicks and rattles minutes after their bottle is tilted. The problem is to get the capsules detaching one or two at a time--too steep an incline "liquefies" the whole inventory and the bottle accelerates. Likewise too full or too empty a bottle, so a math-fun tie-in is to find, given the bottle weight and density of the "fluid", the fill depth which minimizes the height of the center of gravity. --rwg
I give up. After jacking the angle under the vitamin E a fraction of a degree every few hours, a few pills broke loose about 15 min after the last jack (15.0 deg, almost sliding), and a few seconds later a few more, and then more, and the bottle took off. But not rattling a "liquefied" inventory, as I expected. Apparently the pills spread out along the wall of the bottle to form a cylindrical crescent, thereby raising the center of gravity enough to roll nonviscously. I think this would also happen with a drum of pitch if the incline were too steep. A sort of time-bomb. --rwg PS, corrections to my last bicycle gears mail: P D C B ***>*** E-P F G ... . The *only* purpose of the [...] But the hardest part is to figure out how ***to*** reduce the [...] STREPTOMYCIN PYCNOMETRIST