Demos: 2C-10 Bernoulli Cans
Two weighted coffee cans are suspended from the ceiling, a few centimeters apart. When an air stream is directed between the cans, the cans actually swing together, rather than fly apart, illustrating the Bernoulli effect.
Directions: Allow the cans to come to a complete rest, then direct the air stream from the hose into the region between the cans. This should be done carefully. At first, one of the cans may be blown away by the impact of the air, but by carefully monitoring the direction of the stream, the cans can be made to crash together.
Suggestions for Presentation: As in other demos illustrating the Bernoulli effect, ask what will happen if you blow between the cans. Will the cans be blown farther apart? Focus the class attention on the air speeds in each region.
Applications: When two ships, trains or trucks pass each other in opposite directions with little distance between them, they tend to be drawn together.