One last thought on this, you would need to rotate the ball through 270 degrees of a circle for it to fly off in the direction opposite your input, at 180 degrees it would fly off perpendicular to the cart, or if you channeled it back (from half circle) to be opposite your input I would guess Newtonian force would be there. So that negates my idea of why centrifugal motion has no opposition force, I guess the best explanation is it just doesn't. Still think the idea that an unbalanced spinning rotor is the mechanical analogy to a standing wave is a pretty good one though. It is quite silly but I think I am going to have to buy some sort of toy track and a pinball plunger and see if I can't build something along these lines this Fall.