Date: Tue, 17 Oct 2000 13:10:15 -0400

Author: Machele Bailey

Subject: Re: Hoberman Sphere and Conservation of L

Post:

Pictures????? Sounds cool!

Chele

"William W. McNairy" wrote:

> Greetings Tappers--
>
> At the suggestion of a prof in our introductory physics for pre-med course,
> we just constructed an attractive conservation of angular momentum
> demo. Take one (large) Hoberman sphere (see Zany Brainy or other
> children's store). As per enclosed instructions, insert the pulley
> connections into the sphere.
>
> With carpenter's string (braided, about 200 lb test), tie the pulley to a
> ball bearing swivel. This was also a hint from the (angler) professor--
> these swivels available from WalMart fishing area for about \$1.50/3-- works
> much better than traditional brass swivel. Tie the swivel to more string
> and loop the other end of the string through the hook you have in the
> ceiling for the bowling ball pendulum. If you don't have the hook in the
> ceiling for the pendulum, you should. Install one now.
>
> Adjust the height of the sphere to a comfortable level for the prof. Spin
> the fully extended sphere-- then pull on the cord passing over the pulley
> to force the Hoberman sphere to collapse. Angular velocity increases
> rapidly as the sphere collapses to very small size (decrease in moment of
> inertia). Let out the cord to have the sphere enlarge again-- it
> slows. Repeat this process.
>
> Students ooohed and aahhed over this one-- pretty sphere, pretty spinning.
>
> Hoberman spheres available in a variety of colors, including glow in the
> dark models.
>
> Enjoy!
>
> bill
>
> *****************************************
> William W. McNairy, Ph. D.
> Senior Lecturing Fellow
> Room 104I (919)-660-2689
> Dept. of Physics, Duke University
> Box 90305 Durham, NC 27708
> *****************************************

--
Machele Bailey-----Lab Manager-----Wake Forest University

-----"Nothing shocks me. I'm a scientist." - Indiana Jones-----

Back