The floating ball game is an excellent example of "Bernoulli's Principle". As air is forced around the ball it must move faster in order to "catch up" on the other side. The result is a decrease in air pressure around the ball that in turn keeps the ball in place. The force is strong enough to resist other forces acting on the ball such as a subtle tap from your finger. The force can also overcome gravity if the flow of air is strong enough. This can be demonstrated by turning the base of the pipe 15-20 degrees - the ball will remain suspended in the air flow even though it is not directly above it. Give it a try and see what you can discover!
Comes with two styrofoam balls.