In this Kaleideum At Home activity, we show how the floating styrofoam ball demonstrates Bernoulli’s Principle. Bernoulli was an 18th-century Swiss mathematician who discovered that the faster air flows over the surface of something, the less the air pushes on that surface, so the lower its pressure.
Watch the video and then try it at home with ping pong balls or other lightweight balls. The air from the hair dryer flows around the outside of the ball. If you position the ball carefully, the air flows evenly around each side. Gravity pulls the ball downward while the pressure below the ball from the moving air forces it upward. All the forces acting on the ball are balanced and the ball hovers in midair.
If you move the hair dryer, the ball will follow the stream of air. Bernoulli’s principle says that the fast moving air around the sides of the ball is at a lower pressure than the surrounding stationary air. If the ball tries to leave the stream of air, the still, higher pressure air will push it back in. So, the ball will float in the flow no matter how you move.