Lift of spinning objects.

[Scott Goelzer <sgoelzer@COEBROWNACADEMY.COM>]

Hi
Just to quick demo this, take a old bic pen and remove the contents (ink
tube, end cap, cap) leaving a hollow white plastic tube. Place this on
the end of a desk and push down on the tube hard with the end of your
thumb. The tube will squirt out sideways having been imparted with
considerable spin. If done well you can get it to not only rise as it
moves horizontally, but actually loop.

Enjoy,
Scott

> Date:    Thu, 18 Jan 2001 18:56:21 -0500
> From:    "Dwight K. Souder" <crvhs_dks@CRESTVIEW-RICHLAND.K12.OH.US>
> Subject: Lift of spinning objects.
>
>     The other day, I was reading in some old science book about flight.  I came
> across an example I was a little confused with.  The example was how a spinning
> ball was able to generate "lift" by giving it a backspin, in which I have
> observed while playing volleyball or basketball.  They authors gave an
> explanation that it was due to the relative velocity of the top of the ball in
> respect to the bottom of the ball.
> snip

>     Since the bottom of the ball is spinning into the wind, wouldn't it have a
> higher relative velocity in comparison to the top of the ball?  I'm just curious
> how does a backspinning ball "float" while a forward spinning ball "dives".
>
> Dwight
> Ashland, OH

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Scott Goelzer
Physics Teacher
Coe-Brown Northwood Academy
Northwood NH 03261
sgoelzer@coebrownacademy.com
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