Fred Schaal (Lane Tech HS, Mathematics) Screaming Orange Hat
Fred showed his stylish new hat, produced out of Ten Mile Cloth / from Dynamic Textiles, Inc. Phone 718 631 5005 Fax 718 279 4104. He raised the question of the meaning of the label, which used the terms "dominant wavelength between 595 and 605 nm", "excitation purity not less than 85%", and "luminous factor not less than 40%".  The meaning is given in terms of the International Hunter Education Association [IHEA] specifications for "Hunter Orange" garments:

"The IHEA recommends the description of Hunter Orange as "having a dominant wavelength between 595 and 605 nanometers, a luminance factor of not less than 40% and an excitation purity of not less than 85%". Highland guarantees that Ten Mile Cloth, Camo Ten, Easy Ten, and TenAcious meets these specifications."  Source: http://www.ihea.com/_assets/documents/Hunter_Orange_Study.pdf.

Don Kanner (Lane Tech HS, Physics)200 Puzzling Physics Problems with hints and solutions by Peter Gnadig, G. Honyek, K. F. Riley [Cambridge 2001] ISBN 0-521-77480-3
Don found the book interesting and stimulating for the most part, but felt that some of the problems "needed work":

1. Q:  A "black box" has two sets of terminals on each side.  When a battery of voltage V is connected to one side, a voltage V/2 is read across the other side. When the battery is hooked across the other side, a voltage V is read across the first side What is inside?
   A: (But, what about internal resistance of the voltmeter?)

2. Q:  If you push an object and it goes off the table [a distance of 1 meter], does it have wheels?  A:  Yes [Don pushed an empty plastic cola bottle off the table to show the absurdity of this question.]
3. Q:  Why do bubbles in a glass of champagne accelerate on the way out of the glass?  A:  Allegedly, the force of gravity is balanced by the buoyant force.  But then, why would they accelerate at all?

Here is a review from the website http://www.amazon.com.

The problems are generally at the level of International Physics Olympiad competitions or higher, and are very suitable for freshman/sophomore honors physics courses. The problems are tough and very interesting, with many unique and unusual twists, guaranteed to challenge even the best students preparing for physics competitions at the senior high school and undergraduate levels. I would guess that those sitting for PhD qualifying exams will have difficulties with some of the problems. The surprise is that the solutions require no more than elementary calculus, although lots of original critical thinking and insight are necessary. 

Gnadig and Honyek are both leading the Hungarian physics olympiad teams for many years, while Riley is a Fellow of Clare College, Cambridge University. Riley had a previous equally interesting but slightly less difficult problem book called "Problems for Physics Students," covering quite a few interesting Cambridge University Natural Sciences Tripos and entrance exam type questions for the best UK high school students.

If you are a physics buff, you will derive countless hours of enjoyment (and frustration - if you resist the temptation of looking at the provided solutions too soon), plus it will bring your understanding of classical physics to a deeper level. 

A few other worthy physics problem books include Thomas & Raine's "Physics to a Degree" for undergraduates, and Dendy's "Cambridge Problems in Physics" for high school students aiming for Cambridge University entrance. The Russian books "Problems in General Physics" by Irodov and "Problems in Elementary Physics" by Bukhovtsev are very good too but they may be harder to find. An upcoming excellent (and tough) classical mechanics problem book is David Morin's Physics 16 course text at Harvard - still in its draft form but downloadable from Harvard website. 

Bill Shanks (Joliet Central, Physics, Retired) Various Topics

• Fluorescence of Fred's Hat
  Bill used a very bright flashlight to test whether Fred's hat was appropriately fluorescent. The standard test for fluorescence of a fabric is to shine an ultra-violet light on the fabric, and not whether the fabric "glows".  Unfortunately, the flashlight produced too much visible light, so that we could not see the fluorescent glow.  When the room was dark, there was no phosphorescent glow, either.
• Obituary of ISPP Participant Leo Seren Leo Seren, 83; Physicist on the Atomic Bomb Who Turned Pacifist. Leo Seren, 83, a University of Chicago physicist who called himself a war criminal for the role he played in the development of the atomic bomb, died of amyloidosis Jan. 3 at a hospital in Evanston, Ill. Seren had just earned his doctorate from the University of Chicago when he went to work with Enrico Fermi on the Manhattan Project in 1942. Seren was one of 51 people present in an abandoned squash court at the university's Stagg Field on Dec. 2, 1942, when the first nuclear reactor achieved critical mass. Seren's job was to measure the density of neutrons in piles of graphite, uranium and cadmium control rods used to build the reactor.  He worked on nuclear power until 1960, stopping when he reached the conclusion that there was no way to safely dispose of radioactive waste. He began to focus on renewable energy sources, such as solar, wind and water power. In a 1982 speech before anti-nuclear demonstrators at the University of Chicago, Seren spoke of his regret over his role in the Manhattan Project, which led to the devastation of Hiroshima and Nagasaki, Japan, in 1945 and the loss of tens of thousands of lives. He said that if he were tried for crimes against humanity, "I'd plead guilty. And I'd say for mitigating circumstances that at least I decided that I'd never work on nuclear weapons again."
  
• Solar Heating/Cooling (a favorite subject of Leo Seren's)
  Bill and others mentioned various matters.
  • He suggested using a water reservoir [2 meters in diameter, of weight about 30 tons] to store heat energy in the home, to make it warmer in the winter and cooler in the summer. These reservoirs, and even smaller ones, are common in the state of California, where a state income tax credit for passive solar heating and cooling systems existed for years. Roy Coleman said that one friend in California had built an above-ground swimming pool for this purpose.
  • Another plan involved plastic sheeting and piping around a house, with either pumps or gravity feed.
  • A further suggestion involved cold air intakes for fireplaces and furnaces, as well as dampers that automatically close when not needed.  The cold air intake is a major component in reducing infiltration of Radon Gas from the ground.
  • Solar heating and cooling by blowing air over rocks put underneath a house.
• Buckminster Fuller's Dymaxion House in Dearborn Michigan [http://www.hfmgv.org/dymaxion/].
  "The Dymaxion's round shape minimized heat loss and the amount of materials needed, while bestowing the strength to successfully fend off a 1964 tornado that missed by only a few hundred yards. And the Dymaxion only weighs about 3000 pounds versus the 150 tons of an average home!"  Source:  http://www.thirteen.org/bucky/house.html. See also http://en.wikipedia.org/wiki/Dymaxion_house.  There was some discussion as to whether damage in the tornado is caused primarily by the wind itself, or by the debris that is carried in the tornado.  Both are obviously important.  The first effect was illustrated some time ago in SMILE by Bill Blunk by driving a pencil though a sheet of plywood with a CO₂ fire extinguisher.
• Q:  What is a Monolithic Concrete Dome?
  A: (given by Ann S Bosley: http://www.bizjournals.com/birmingham/stories/2000/07/31/focus3.html)

  The Monolithic Concrete Dome is a super-insulated, steel-reinforced concrete structure. David B. South, president of the Monolithic Dome Institute, and his brothers, Barry and Randy South, developed an efficient method for building a strong dome using a continuous spray-in-place process.
  In 1976, following years of planning and development, they built the first Monolithic Dome in Shelley, Idaho. Since then, Monolithic Domes have been constructed for homes, schools, gymnasiums, churches, offices and bulk storage facilities in 45 states and in many foreign countries.

  Briefly, here are the steps involved in building such a dome:

  • The Monolithic Concrete Dome starts as a concrete ring foundation, reinforced with steel rebar (reinforcing bars). Vertical steel bars embedded in the ring are later attached to the steel reinforcing of the dome itself.
  • An Airform, fabricated to the proper shape and size, is attached to the concrete base. Using fans, the Airform is inflated, creating the shape of the dome. In fact, the fans run throughout construction.
  • Approximately 3 inches of polyurethane foam insulation is applied to the interior surface of the Airform. entrance into the structure is made through a double-door airlock, which keeps the air pressure inside at a constant level.
  • Steel rebar is then attached to the foam using special hooks embedded in the foam.
  • Shotcrete, a special spray mix of concrete, is applied to the interior surface of the dome. The steel rebar is
    embedded in the concrete. The fans are shut off after the concrete is set.
  According to the Monolithic Dome Institute, the advantages of building a Monolithic Concrete Dome include
  the strength and permanence of the structure, energy efficiency, cost effectiveness, attractiveness and disaster
  resistance.
  See also the website http://www.monolithicdome.com/.
• Solar Radiation
  Meteorological winter is defined as the period December 1 - March 1, because this is the coldest period of the year in the northern hemisphere. Why? Precisely why is it colder in the winter than in the summer?  Graduating seniors at Harvard a few years ago incorrectly suggested that the earth is closer to the sun in summer than in winter.  A good physics student might refer to the "glancing incidence" of sunlight in winter, but does s/he know what that means?  The total solar flux is about 1400 watts per square meter, as measured for normal incidence.  The angle of the sun with the vertical  in Chicago varies from q = 42°+23° = 65° in winter to q = 42°-23° =19° in summer.  As a consequence, the solar energy delivered to the ground is 1400 ´ cos q Watts/m², which varies from 1324 Watts/m² [summer] to 591 Watts/m² [winter].  Bill illustrated the role of the angle of incidence using his bright flashlight and white paper. The paper was definitely brighter when the light shone directly on it.  In a similar vein, snow cover melts more quickly where it has a southern exposure, because of the heat absorbed from direct sunlight.

Arlyn Van Ek (Iliana Christian HS) Why are there headrests on automobile seats?
Arlyn put this question on a test recently, expecting students to say that they would provide protection from "whip-lash" in rear-end collisions.  However, many students commented that they would also protect in front-end collisions, as well.  Namely, the occupant's head goes forward, bounces off the air bag, and then snaps backward, to be stopped by the headrest.  Is this correct?

Notes taken by Porter Johnson