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The Bernoulli Challenge

Students learn about the Bernoulli effect with an amusing feat they cannot accomplish.

Bernoulli's Principle: as the speed of air increases, the pressure of that air decreases.

When you blow through the funnel, a current of fast moving air is created around and above the ball. This results in a low-pressure zone below the ball relative to its surroundings. The higher pressure air surrounding the funnel pushes the ball down and keeps it from rising any farther. The ping pong ball cannot be blown out of the funnel.

On the other hand, if you blow across the top of the ball, a low-pressure zone is created above the ball relative to its surroundings. The higher pressure air below the ball lifts up the ball.

If a steady source of air can be blown into the narrow end of the funnel (such as air being released from a large balloon), the funnel can be inverted without the ball falling out. The higher pressure room air pushes up against the ball harder than the fast flowing, low pressure air from the balloon.

The Bernoulli Principle and an Air Cannon!

Objectives

  • Explain how air pressure works.

  • Describe the Bernoulli Effect

Materials

  • Per Demo:
    ping pong ball
    funnel
    large balloon (optional)
    elastic (optional)

Key Questions

  • Based on Bernoulli’s principle, where are the high-pressure and low-pressure zones when you blow through the funnel?What is keeping the ball in the funnel?

What To Do

  1. Write out Bernoulli’s principle on the board.
  2. Select a student volunteer and place the ping pong ball in his hand. Ask him to blow the ball off his palm (easy).
  3. Place the ping pong ball in the funnel and ask the student to tilt his head back and blow the ball out of the funnel. The ball will stay in the funnel.
  4. Get a different student volunteer to try.

​Teacher Tip: For the best visibility, have the volunteer lie face-up on the floor.

Extensions

  • To test your theory, where would you have to blow to get the ball out? Some may suggest that to get the ball out, you have to blow across the top.
  • Invite a student to blow very hard over the top of the funnel. They may be able to blow hard enough to blow the ball out of the funnel. If not, they should at least notice that the ball jumps up the side of the funnel.
  • Blow up a large balloon, attach it to the funnel and, with the ball in place, let it start to deflate slowly. You should be able to turn the funnel upside down without the ball falling out.

Other Resources

Science World | YouTube | How to Explore Bernoulli’s Principle with Two Pieces of Toilet Paper

Exploratorium | Bernoulli Levitator