Why does a ping pong float with a hair dryer?

Answer 1

When you point a running hair dryer upward, and place a ping pong ball in the air stream, it will eventually float somewhere above the hair dryer and near the air stream. It stays above the dryer because the drag of the air balances out the ball's 2.7 grams of mass, and near the air stream due to the Bernoulli effect. The Bernoulli effect is the drop in pressure when a fluid's velocity increases; you can demonstrate it by blowing over the top of a piece of paper. It is partly responsible for the lift generated by an airplane's wing. The ball is drawn towards the center of the air stream due to the increasing velocity and the resulting Bernoulli force, but is pushed away by the air glancing off its surface. The ball maintains a position where these forces balance out, perhaps wobbling back and forth so the average forces balance out.