Air Ball

What It Is

An air pump hooked up to a cylinder; a pool cue with a dowel rod for a handle.
Air_Ball2.jpg

What You Do
Turn it on! Grasp the ball by the handle, place it in the cup, and give it a twist. It keeps spinning! Try holding the handle at different angles (e.g. straight up, 45 degrees, etc.) and see what happens. We have handles of multiple lengths -- does this change anything?

What You Learn

TK

How You Make It

Hook a pump up to a plastic cup and place the ball in the cup.
To make the ball: we used a drill press to drill a hole halfway through the pool ball. We cut a dowel rod to an appropriate size, got some good glue, and cut tracks into the handle so that the glue would not get pushed out.

What We've Learned

The pump needs to be relatively strong and to have a good seal.

DIsplay Sign Text

What to do: Take one of the colored balls, and set it in the cup. Turn on the air pump. The ball should now be floating on a cushion of air. Now, spin the dowel in the ball like you would spin a top and watch what the ball does. Some of the balls do simple spins, and some are pretty crazy.
What is Happening: The balls float on a cushion of air, and so can spin freely. This means that they will spin like tops, or like the earth spins on its axis. When you spin the balls, watch the axis of the spin which is where the dowel is. (On the earth, the axis goes through the north pole, of course!) The axis moves around in a circle. We call this precession. (The earth’s axis precesses too, but very, very slowly.) And that crazy wobbling that you see sometimes? This is called nutation. The earth’s axis nutates as well - though only a very small amount.

Related Projects

What Keeps the Ball in the Cup?

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