The Stacking Blocks demo is called by the title: Tower of Lire. It is PIRA
Demo # 1J11.20. Although the UTexas Lecture Demo website shows a photo of
the demo, it was not set up properly for the photo because the full
extension would alter the cropping space. Nonetheless, I recomend that you
consider starting there in your quest for background info.
From that location you can click on Mechanics (1Axx.xx) and begin scrolling
down to 1J11.20. A link will take you directly to this demo with a photo
of the 4 x 4's we use and an early drawing from UMinnesota.
However, I reommend that you go back to the UTexas homepage and search
several of the more complete websites (we cater primarily to offering the
PIRA 200 most commonly used demos, of which this is one). At the bottom of
the UTexas webpage is a link to "demo resources at other univesities".
I would definitely look at Dick Berg's site at Maryland or (formerly) Keith
Warren's site at NCSU. Dick had his own numbering system (in place before
the PIRA scheme was created about 15 years ago) so you will have to first
guess the title, and then look up the demo. Once there, you will see the
cross reference to the PIRA Demo Classification Scheme (DCS number), which
will confirm the correctness of the choice. Dick placed much of the PIRA
Bibliography references as links to his page.
AAPT is hopeful that the full bibliography will be accessable on their site
in the very near future. We started with 7500 demo references in our
initail quest for a Dewey decimal like numbering scheme (PIRA DCS).
I know that one of the references in the PIRA Bibliography gives a full
explanation of the series, and its L/2N limit for step size when using N
blocks to set up the demo.
Regarding the cantilever/arch issue. Two such "cantilever-like"
structures placed as mirror images of each other result in the classical
architectural arch, or the bridge without pillars in the water. An
interesting extension is the "fake hyponotic rigidity" demo (human bridge)
in which the weight of the person standing on a person suspended at head
and feet across two stools is resolved onto the chairs.
I hope this helps. Karl
Dr. Karl I. Trappe Desk (512) 471-4152
Lecture Demonstration Office Office (512) 471-5411
Physics Department, Mail Stop C-1600 Home (512) 264-1616
The University of Texas at Austin
Austin, Texas 78712-1081