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#3
01-14-2019, 11:22 AM
 Guest Join Date: Feb 2009 Posts: 14,812
As an alternative, consider those circus acts where one or more motorcyclists are going in circles on the interior of a big mesh ball (cage). What would happen if the motorcyclist sat still and the cage spun under him? He would not upside down hang in mid-air.

The motion of marbles, pennies, or motorbikes depend on their movement. The coin spirals (and would work the same with marbles or anything that moved smoothly) rely on the motion of the object - it gains momentum then wants to go in a straight line. the surface of the spiral chamber forces it to curve, and that is the apparent centrifugal force that keeps the coin spiralling.

Of course, the small amount of friction could begin to drag the marble along until it is spinning with the funnel container. The closest real-world analogy would be a roulette ball; by hitting the spinning wheel surface and being impacted by the irregular surface, it gains momentum that causes it to spin with the wheel, until it has more momentum that the wheel (less friction between rolling metal ball and surface than between wheel and table.) At that point it continues rolling while the table under it slows down.