If you have a coin on your hand, it won't just float. Instead, it will shoot up towards the ceiling because the ride car is moving down much faster than a falling coin. The downside is that it will eventually fall and probably smack someone on the head. A dime might be a better choice if you can spare the extra nine cents because it will hurt less on the noggin that it lands on. Of course, I would never actualy do anything like this. I'm just talking about a theoretical experiment. However, if you find any loose change on the ride, well, I seemed to have misplaced a few coins.