Floating In Air

Explore 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 ceiling. Make 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?

What's the Science?
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.

What 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.

Want More?
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 small balloon.
- 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 Challenge!

When you're at the California Science Center, be sure to visit the Air Pressure Cart in the Disney Court.