Eject a Ping Pong Ball with Your Breath

Let's take a look!

Watch the video on YouTube.

What kind of experiment is this?

Experimental procedure and explanation:

• Place a ping pong ball into a cup and blow into the cup.
• When you blow from the top at an angle onto the inside wall of the cup, the ping pong ball flies out of the cup.
• The ball advances while riding on the flow of air and receiving drag (a force that works in the direction of flow and includes factors such as air resistance) and flies out of the cup.
• As with “Floating an Egg,” when the gap between the container wall and the object (such as an egg or a ball) is relatively small and a flow is applied directly above the object, the increase in pressure that occurs when the flow is turned back is used to lift the object. However, when the gap is large, another method that can be used to apply a flow along the wall of the cup, as in this experiment with a ping pong ball: use the drag that is created to eject the ball.

[Keywords]	air resistance, drag, pressure vortex, ring vortex
[Related items]	Floating an Egg
[Reference]	“Illustrated Fluid Dynamics Trivia,” by Ryozo Ishiwata, Natume Publishing, pp.54-55 and 62-63 “The Wonders of Flow,” Japan Society of Mechanical Engineering, Kodansha Blue Backs, p.15