Fun Party Trick

Interesting explanation Conder, to be honest I hadn't thought it through this way but this makes a lot of sense. Seemingly this trick would also work in vacuum based on this reasoning.

The rate of rotation of the flipping coins must be the consistent variable here, which is directly related to gravity. The release of one end of a coin initially gripped at both ends would initiate a rotation rate determined by gravity and some dimension(s) of the coin. Maybe later I'll sit down later to work out the analytical expression.

Another idea, not mutually exclusive, occurred to me. It is hard to get the center coin completely centered. As the coin fall, there will be air resistance which would be an upward force slowing the coin. If the smaller coin is not centered, the resistance may impact the side of the quarter without the middle coin more than the other side. This will cause the flip, and might also abate once the smaller coin is on the bottom.

Not sure if things really work like that, but seems plausible.