Having just learned about air and atmospheric pressure
when we made a DIY
barometer, this lesson served as a great extension.
All you need is a ping pong ball and a working hair
dryer.
I had one son hold the hair dryer straight up, while it
blew cool air at the highest setting. Our other boy gingerly moved a ping pong
ball into the air stream.
WHOA! They were amazed to see the ball float in mid-air
without falling. Even more fun is when they moved the hair dryer at a slight
angle to see the ball still stay suspended!
Why it Works
The force of air from the hair dryer will push the ball
up, and the force of gravity will push it down. It will stay suspended at the
point where the force pushing up and gravity pulling it down are equal.
The reason the ball does not shoot out of the stream of
air, is air pressure. The air coming out of the hair dryer has a lower air
pressure than the air surrounding it. This keeps the ball within the column of
fast-moving air coming from the dryer. This principle was discovered by
Bernoulli in the 1700s, long before the first hair dryer was invented.
No comments:
Post a Comment