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Erich, good idea on the pencil trap. You can collect a lot of coins that
way!  Have you tried a grid matrix like those used on wind tunnels to smooth
out the air flow?

;-)

It makes me wonder how kids interpret this exhibit (besides "bernoulli"
makes things fly, like "magic").  They probably wonder why the ball doesn't
just blow away. You are probably doing well if they understand the forces in
the vertical direction; that the ball doesn't move because the force of lift
matches the force of gravity.

Looking at the forces left to right, you have to start visualizing the air
streams, and how they provide "negative feedback": as the ball tries to
escape, the air streams compress, pushing the ball back to the center.

I've seen streamers attached to the blower, but I don't think they really
capture what the air streams are doing.

For visualizing air streams, I wonder how a 2D version would work?  Picture
a visible stream of liquid holding up a bouyant object... (like those
hand-held water squirter toys where you have to get the balls through the
hoops).

Or a virtual blower on a monitor to complement your real blower: Here's a
nice flash simulation showing the air stream as you tilt the blower at an
angle.  Could be made into a game with a fun objective, like trying to
transfer different size balls that fall from the ceiling without dropping
them.

http://www.edumedia-sciences.com/en/a205-lift

Good luck!
-Eric

Eric Yuan
Newmarket, NH

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