Hi. This forum seems to be just what I'm looking for! My friend and I have just been having one of those drawn out debates over a hypothetical physics model and I guess (although it was an animated discussion) neither of us was 100% convinced we were correct what we were saying. We were both pretty adamant the other person was wrong though ;) The basic hypothetical situation is a hovercraft hovering over a moving conveyor belt. Does the hovercraft move in the direction of the belt, or does it remain stationary (relative to everything else in the universe)? We tried thinking of it as a mathematically perfect model. Or at least with these constraints: The workings of the ‘hovercraft’ are unspecified, but you can assume it pushes air downwards from a skirt and is completely stable.. ..on unmoving ground it would appear completely stationary. The conveyor belt is a huge (maybe even infinite) plane, moving at a constant velocity. The ‘craft’ has just magically popped into existence above it at a stable altitude. Actually, feel free to toy around with the restraints all you like if you have any comment to make :) This came about because my friend was playing a console game where his character, riding a ‘hoverboard’ glides onto a conveyor belt for a few moments. The character is pushed along as though he had stepped onto the belt. Obviously wrong. My friend said that the belt should not affect the board at all. I said I thought it would, a bit, after a fashion. He said it never would. Well my thinking was that if the board is *hovering* over the belt then it is using thrust to overcome the effect of gravity on its mass. I.e. there are forces acting directly upwards and directly downwards which are equal and opposite, so the hoverboard remains in place. I thought that this made the two things connected, albeit loosely (the conveyor belt isn’t frictionless, after all), so eventually the relentless motion of the belt would be transferred through the column of air to the board. Now my brain hurts. Please help!