Concepts

Bernoulli's principle

Overview

A ball is placed in a funnel and the funnel is connected to a reversed vacuum cleaner that provides a continuous supply of air. As the air flows out out of the funnel at a high velocity, the pressure difference created by Bernoulli effects keep the ball from being blown out of the funnel. Using the same idea, when a ping pong ball is placed in the smaller funnel, the low pressure created by the high velocity air going around the ball will keep it in the funnel, even when held upside down.

Details

Equipment

• [1] Reversed vacuum cleaner
• [1] Large plastic funnel
• [1] Small glass funnel
• [1] Small air hose
• [1] Medium-sized ball
• [1] Ping pong ball

Classroom Assembly

1. Connect the reversed vacuum to a power source or connect the hose and the glass funnel to an air supply.

Important Notes

• Ensure demo will not be place beneath low-hanging lights or low ceiling

Script

For a large class, this demo can be done with the plastic funnel and vacuum. For a small class, the glass funnel with air supply can be used. Substitute the appropriate apparatus in the instructions.

1. Place a medium-sized ball on top of the vacuum cleaner.
2. Turn on the vacuum. Notice that the ball is floating in the air.
3. Turn off the vacuum.
4. Attach a funnel to the output of the reversed vacuum.
5. Turn on the vacuum.
6. Place the same ball just above the funnel. The ball should float in the air, as before.
7. Turn off the vacuum.
8. Place the same ball in the funnel.
9. Turn on the vacuum. Notice that the ball is not floating in the air. Counterintuitively, it is held inside the funnel by the upward stream of air.
10. Turn off the vacuum.
11. Place the same ball on the table.
12. Cover it with the upside-down funnel that is connected to the vacuum.
13. Turn on the vacuum.
14. Raise the funnel. Notice the ball is held inside the funnel and is supported by air streaming out of an upside-down funnel.
15. Turn off the vacuum.

Additional Resources