Demos: 2C-04 Ball in Tube

A large glass tube, open at one end and connected at the other to an air supply, has a light plastic ball inserted into the open end. The ball is allowed to fall to the other end of the tube. The air supply is turned on and the ball, rather than being blown out of the tube is held tightly against the end by the air flowing around the ball. The tube can actually be inverted and the ball will not fall out. This phenomenon is explained by Bernoulli’s principle.

Directions: With the air supply hose attached to the tube, drop the ball into the tube. Turn on the air supply. The ball will be seen to spin at the bottom of the tube. Carefully invert the tube and the ball will remain in place.

Suggestions for Presentation: Place the ball on the table and ask the class what would happen if you were to direct a stream of air at it. Then ask what happen if you placed the ball in the tube and turned on the air supply. Many will guess that the ball will be blown out of the tube. After seeing the results, ask how this might be explained.
NOTE: This demo can be done on a much smaller scale. Invert a small plastic funnel and place a ping-pong ball against the mouth of the funnel. Blow very hard through the stem of the funnel and simultaneously release the ball. It will be held in place.

Applications: None evident

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