Demonstration #1

PURPOSE

To illustrate the Bernoulli equation, which states that increased velocity over one surface of a thin material will create a pressure differential.

PROCEDURE

1. Cut the cardboard into a disk about 8" in diameter.  Cut a round opening in the center which will allow the disk to fit tightly around the nozzle of the hair dryer.   (The cardboard is used to create extra surface area and doesn't affect the principles being demonstrated.)
2. Stick a thumbtack through the center of a piece of paper with the point facing up.   (The tack is used to keep the paper under the flow of the hair drying and is otherwise unrelated to the experiment.)  Lay the paper on a desk.  With the cardboard in place, turn on the hair drying and direct the flow of air straight down on the paper.  The increase in the velocity of air above the paper will cause a lower pressure on top of the paper than on the bottom.  The air flow should pull the piece of paper up onto the hair dryer rather than blow it away.  (NOTE:  Experiment with this procedure before demonstrating it to the class.)