air pressure with this fun activity that promises to keep
even the most serious scientists amused for hours!
You Will Need:
- Hair Dryer
- An empty toilet paper tube
- A ping pong ball
What to Do:
Turn the hair dryer on high and point it toward the
sure to use a cool-air setting!
What do you think will happen if you gently place the
ping pong ball into the stream of air? Will it blow
away, drop to the floor or float? Try it and see.
Try walking slowly, tilting or jiggling the hair dryer.
What happens to the ball?
Now try slowly lowering an empty toilet paper tube over
the ball. What happens now?
You are using air
to lift the ping pong ball. How? By controlling a force
called air pressure. Pressure is what we call it when
something pushes on something else. When you squeeze a
grape, you are putting more pressure on the grape. Even
though we can't see it, air pushes and squeezes things
all around us - including our own bodies! We rarely notice
it, because we are used to it, and our bodies are built
to push back. Things like tires, airplanes and sailboats
all work because of air pressure's push.
you've just seen is an example of what's called Bernoulli's
principle. Bernoulli, a Swiss scientist who wanted to
find out how these things work, discovered this effect
more than 250 years ago. He found that the faster air
slips past the surface of something, the less the air
pushes on that surface (and so the lower its pressure).
When you place the ball in the stream of air created by
the hair dryer, you force the air to flow around the ball
and create an area of lower pressure. The still air surrounding
the air stream has more pressure and pushes the ball to
keep it snuggled in the stream.
When you place the empty toilet paper tube
into the air stream, the air is funneled into a smaller
area, making air move even faster. The pressure in the
tube becomes even lower than that of the air surrounding
the ball, and the ball is sucked up into the tube.
See what happens when you:
- Try tubes that are longer or shorter or wider or skinnier.
- Try to float other objects in the air stream. Try a
- Try to float two or more balls in the same air stream.
How many can you float at once? How do they behave when
there is more than one?
Or try the Funnel
When you're at the California Science Center, be sure
to visit the Air
Pressure Cart in the Disney Court.