The table tennis ball is suspended, or flies, above the air stream emitted from the hair dryer. The initial force of the moving air from the hair dryer pushes the ball up. Once in the air, gravity pulls the table tennis ball back to Earth. The fast-moving air below and around the ball, however, creates areas of high and low pressure that give the ball lift. Airplane wings are designed to achieve lift.
Air flows faster over the curved top part of wing than the straighter part below the wing.
In the case of the table tennis ball, lift and gravity balance each other, enabling the ball to remain suspended. It may take a few tries to get the table tennis ball to fly successfully. Students can try to explain why sometimes the ball remains suspended in the air stream and why sometimes it shoots out of the air stream. When students increase the speed of the hair dryer, the table tennis ball's height above the hair dryer increases due to the additional force and lower pressure of the faster-moving air. When a balloon is placed in the air stream, it will be suspended at a higher distance than the table tennis ball due to its lighter weight.