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Re: Lift of spinning objects.



I always demonstrate this phenomenon using a Wham-O toy called, I think,
"Trak Ball". It is in principle like a jai-alai cesta and pelota, but it
uses a clever plastic cage with a serrated track and a larger ball of
styrofoam. It requires no skill to throw inverted curves using this
device. I always bring it out when I talk about parabolic trajectories
(yeah, I like jokes) but I never try to explain its physics - or
airplane lift, either. I find Hewitt style explanations of these
phenomena conceptually vacant. I have another version of this toy, a
Taiwanese ripoff called "Trail-Ball" at home. It's a great toy which can
be used to amuse children, as well.

(No, I don't even know if Hewitt treats lift, but I'm prepared to doubt
that he does so valuably. No other elementary textbook I've seen does
any better.)

Leigh