High School Mathematics-Physics SMILE Meeting
10 May 2005
Notes Prepared by Porter Johnson

Information

Roy Coleman appeared on the Channel 5 (NBC) news on Monday 09 May. His classroom work with college-bound students was shown on that program, in keeping with his wide-spread, well-deserved reputation as an excellent physics teacher. You looked great, Roy!

Leticia Rodriguez [Peck Elementary School] Evaluation of CERAGEM Thermal Bed
As outlined at the SMILE meeting of 08 March 2005, mp030805.html, Leticia evaluated the claims for this Acupressure Thermal Bed with Jade rollers, based upon her own experience this spring. Here is her evaluation:

Thesis:	CERAGEM Thermal Bed can help maintain your health. The device involves "deep heating" with an infra-red light source.
Procedure:	Try it for several 30 minute sessions. It is alleged to relieve pain, and promote "detoxification".
Data:	In the initial phases of the treatment, she developed a skin rash. After several sessions, the rash went away. She found it to be relaxing.
Conclusions:	Leticia felt better because of the experience. It seemed to improve her circulation. Her chiropractor noticed an improvement on posture and reduced tendency toward osteoporosis.

The general feelings of the group may be summarized as follows:

Massage therapy is a standard means of promoting healing and improving muscle tone.
Deep infra-red radiation is likely to produce physical symptoms similar to "prickly heat" obtained in the summer sun.
Any means of improving muscle tone and promoting exercise --- particularly aerobic exercises lasting over 30 minutes, will produce significant cardiovascular benefits.
Any claims of "detoxification of the body" are rather far-fetched, difficult to believe, and challenging to prove. Simply put, infra-red radiation in the body does not seem to destroy toxins in the system.

Porter Johnson commented that the increase in longevity in industrialized societies over the past century is generally attributed to advances in medical sciences --- as vaccines, miracle drugs, and diagnostic tools. On the other hand, advances and improvements in sanitation, availability of nutritious food, refrigeration, and the like are equally important. Civil engineers are just as valuable as the medical profession in improving the length and quality of life.

Thanks, Leticia.

Bud Schultz [West Aurora HS, physics] Dots and Lights
Bud detected the large electric fields that are produced in the vicinity of a Vandergraaf Generator by bringing gaseous discharge tubes, which contain gases such as neon, close to the generator. We saw a very impressive display of red light from an ordinary neon tube! Fluorescent tubes (which contain mercury vapor) are available in 2 feet and 18 inch lengths, for more convenient experimentation. For more information see The History of Electrostatic Generators: http://www.hp-gramatke.net/history/english/page4000.htm. Bud showed us how to produce both positive and negative charges by rubbing objects together.

Bud next illustrated how to find Powerpoint™ lessons using the usual search engines, by searching for, say, hubble + ppt. The following presentation, along with many others, appeared: Collisions in Space: http://science.howstuffworks.com/dictionary/astronomy-terms/space-collision.htm and A Brief History of Cosmology: http://www.astro.umd.edu/~miller/teaching/astr422/lecture02.pdf. Caution: Particle Data Files files, which are of the form *.pdf, are often very large, and require a fast browser for viewing.

Thanks for the info and ideas, Bud!

Larry Alofs [Kenwood HS, physics] Stirling Engine
Larry show us the AJS 66415 Stirling engine model https://www1.fishersci.com/Coupon?cid=1341&gid=2368582&details=Y, which he had obtained from Fischer Scientific: https://www1.fishersci.com/. The following description is given:

"Heat from a small candle sends this Stirling engine model into oscillation almost immediately. Easy to construct, this unit demonstrates the Stirling engine principle. A test tube acts as the cylinder and four marbles work as a transfer piston."

Our device, which consists of a test tube of outside diameter 18 mm with four marbles inside, pivots about a center with balloon stretched over a rubber stopper that is tightly pushed into the opening. When the bottom of the test tube is heated with a candle, the air inside expands, and fills the balloon, which is tucked under the test tube near the fulcrum, causing the tube to tilt. The marbles then roll to the other end of tube, the air inside cools, and the test tube tilts back again. Under proper conditions the process repeats itself every second or so, the device acting as an engine. We were disappointed with the operation of our engine --- the breezes in the room may have prevented its proper action.

For additional information on Stirling engines, see the American Stirling Company website: http://www.stirlingengine.com/

Physics at work! Thanks, Larry.

Bill Shanks [Joliet Central, retired] Ray-tracing on Blackboard Made Easy!
Bill showed the Stanley 45-101 MaxStick Straight Edge [found here], which he had obtained recently at Menard's. It was marked in inches through 24", but could easily be modified by pasting on a 60 cm metric scale. He attached flexible magnetic strips to the back, so that it could be used for blackboard optics, as well as other things. He used the MaxStick for illustrating refraction, Snell's Law, mirages, total internal reflection, and a two-dimensional corner reflector. Then he showed ray construction for a thin lens, laying out the symmetry axis, the plane of the lens, and the location of the principal foci. Bill recommended the term "principal focus", rather than "focal point" to describe the point at which parallel light is focused by a converging lens. He illustrated that the images from a simple converging lens are always inverted. In particular, the images on the retina of the eye are inverted, and the brain corrects for that. He called attention to some experiments with Upside Down Glasses http://www.madsci.org/posts/archives/mar97/858984531.Ns.r.html, which indicated that it takes over a week for the users to see "normally" with these glasses.

Good teaching tips! Thanks, Bill.

Porter Johnson and Earl Zwicker [IIT, physics] Newton's Third Law
Porter found an old fan cart (propeller-driven, four-wheel cart) with a very corroded battery case, which he rejuvenated through liberal application of WD-40™ solvent, toothpicks, Q-tips, and elbow grease to remove the corrosion. Roy Coleman mentioned that WD-40 was developed in the Atlas Missile Program http://www.au.af.mil/au/awc/awcgate/au-18/au18004f.htm, from which the following has been excerpted:

"As a sidelight, during development, designers determined that the Atlas needed corrosion protection from the salt-laden Cape Canaveral air. Convair chemists worked on many formulas to provide a wipe-on protection. This endeavor led to the development of WD-40, (water displacement formula, trail number 40) which now has worldwide applications."

The rejuvenated fan cart worked very well at the SMILE meeting. It had ball-bearing wheels attached to the base, and the battery pack had six 1.5 Volt C-Batteries. In addition there was a switch to activate the small motor, which drives a propeller (fan) with two plastic blades about 10 cm long. Earl put the cart through its motions, using it to show basic concepts in mechanics:

First he held the cart in place, and turned on the fan. He used a short piece of string to show the direction that air was blowing.
He put the cart on the table and turned on the fan, and asked us to predict what would happen when he released the cart.-- The cart accelerated across the table.
Then he put a cardboard baffle on the cart in front of the fan. What happened next? Well, not very much -- The cart barely moved at all. How come? When he put a larger baffle on the cart, the cart did not move at all. Why?
He took off the large baffle and held it between the fan and the small baffle still attached to the cart. Then what happened? The cart took off once again. Newton's Third Law works!

For additional details, including a picture, see the SUNY Stony Brook website http://naples.cc.sunysb.edu/CAS/pdemos.nsf/By+Course+Number/C.+Kinematics+And+DynamicsC5.+Third+Law+Of+MotionC5-18Fan+Cart, from which the following has been excerpted:

"With the sail unmounted, turn on the fan and release the cart; it moves in the direction opposite to that of the blowing air. Mount the sail and blow into it with your breath; it moves in the direction which you are blowing. Finally, with the sail in place turn on the fan and release the cart.
Q: What will the cart do with the sail in place and the fan operating?
(a) move in the direction of the air,
(b) move opposite to the direction of the air, ... or ...
(c) remain at rest.
A: It will remain at rest."

An oldie but a goodie! Thanks, fellows.

Fred Schaal [Lane Tech HS, mathematics] There May Be Dark Matter in Your Living Room
Fred called attention to the fact that, according to current theories of cosmology, dark matter should exist. This dark matter interacts very weakly with ordinary matter -- only through gravity, and not the electromagnetic field. In other words, we can't see it, but it may permeate our galaxy. In particular, the flux of dark matter through the earth is estimated to be 10⁶ particles per square-meter per second. But ... We don't feel a thing!

Wow! Thanks for the info, Fred.

See you next September!

Notes prepared by Porter Johnson