Learning Lesson: Going with the Flow

Overview

Bernoulli's principle states that in fluid flow, an increase in velocity occurs simultaneously with decrease in pressure. The students will discover that the faster air moves (air acting as a fluid), the lower the pressure becomes within that flow of air. They will see this effect blowing between two soda cans.

TOTAL TIME 5 minutes Two (2) empty soda cans, a level surface None None Tornado safety

Procedure

1. Lay the two cans parallel to each other, about one inch apart, near the edge of a level surface.
2. Put your face down near the surface and blow lengthwise between the two cans.
3. It will take some trial and effort but eventually the two cans will roll together.
4. Another way of demonstration is by suspending two cans with string about an inch apart and having the student blow between them.

Discussion

The affect is Bernoulli's principle in action, named after the Dutch/Swiss mathematician/scientist Daniel Bernoulli. By blowing between the two cans, you are making the air between them move faster than the surrounding air (which is basically calm). The cans roll together as the higher pressure surrounding the two cans (away from the air flow) pushes the cans together toward the region of lower pressure.