Bernoulli's Principle - Dancing Soda Cans and Jumping Coins (Debbie Brenner, Rena Benor)

Author

Rena Benor, modified by Debbie Brenner

Principles Illustrated

Standards

• NGSS Science & engineering standards

  • Asking questions

  • develop and using models

• NGSS Cross-cutting concept standards

  • Cause and effect

  • systems and system models

  • energy and matter

  • stability and change

• NGSS Disciplinary core idea standards

  • From molecules to organisms (HS-LS1)

  • ecosystems: Interactions, energy and dynamics (HS-LS2)

  • Earth and human activity (HS-ESS3)

  • Matter and Its Interactions (HS-PS 1)

Materials:

Jumping Dimes:

Dime for each student or group

Plates of substantial weight (not paper), one for each student or group

Dancing Cans:

2 empty soda cans for each student or group

Questioning Script:

Jumping Dimes: Use your knowledge of the properties of gases, forces, and pressure to find a way to put the dime onto the plate without touching either object.

Dancing cans: Blow air between the two cans. How do you think the two cans will move, if at all?

Prior knowledge & experience: Air pushes objects apart

Root question:

Jumping Dimes: Using the concept of air pressure, can you predict a way to get the dime onto the plate?

Dancing Cans: What do you think happened to bring the two cans together?

What could have caused a decrease in air pressure between the cans?

Target response:

When a ball or other curved object is placed in an air stream, the air will increase its speed as it moves around the outside of the can. This happens because the air has to travel a further distance to get around the can and meet back up on the other side of the can. The connection between air speed and air pressure is at the center of Bernoulli's Theorem. When the air increases its speed as it moves around the ball, the air pressure around the ball also drops. In the places where the air moves the fastest, the air pressure is also the lowest.

The low air pressure around the cans pull them together. When a student blows hard on the can, you increase the speed of the air around it. This also causes the air pressure to decrease, which then pulls the cans even closer.

Common Misconceptions:

Jumping dimes: Students predict that blowing across the top of the dime will push the dime forward or do nothing at all.

Dancing cans: Students predict that the cans will be blown apart.

Real World Applications:

Because they understand Bernoulli's principle, engineers manipulate air pressure in their designs to control and stabilize everything from rockets to helicopters to blimps. When designing airplane wings, engineers shape them so that they create lift. Even cars and trains are designed to take advantage of this principle, helping moving vehicles to stay on the ground at high speeds.

Videos:

References

Teach Engineering: Fun with Bernoulli

NASA: Bernoulli's Principle

Bernoulli's Principle: Advanced Discussion (includes algebra and calculus)

Bernoulli's Principle: Simple Discussion