Session FB20 - New Teaching Techniques.
ORAL session, Monday afternoon, March 22
Room 311E, GWCC

[FB20.01] CPEP: The little nonprofit with big ideas

The Contemporary Physics Education Project (CPEP), formed over a decade ago, has produced high-quality educational meterials for use by teachers who wish to incorporate contemporary physics into their teaching. This presentation will review CPEP's efforts in nuclear physics, particle physics, and plasma physics.

[FB20.02] Transition from Introductory to Advanced Courses

The gap between the level of introductory physics courses and the first upper-level course in mechanics and/or electromagnetism is unreasonably wide. I will discuss some steps taken at Illinois State University to narrow this gap.

[FB20.03] Wavelength or Frequency?

Wavelength and frequency are often used interchangeably. Sometimes, however, use of one instead of the other can lead to spurious conclusions. When light interacts with matter, frequency, not wavelength, is the physically significant quantity. Snell’s law provides a good illustration, blackbody radiation another. Many astronomy textbooks argue that the human eye has evolved to act as a kind of “solar Wien peak detector”. Rods in the human eye have peak sensitivity in the green at about 507 nm. Using Wien’s displacement law with the effective solar blackbody temperature of 5770 K, the solar flux is found to peak at a wavelength of 503 nm. Therefore, they conclude, the human eye evolved to match the solar Wien peak. This astronomical argument is, at best, misleading - even more so since the effective blackbody temperature at Earth’s surface is not 5770 K. The solar blackbody spectrum, evaluated as a function of frequency, has a peak at about 340 THz - in the near infrared. This Planck frequency peak is the appropriate referent since the eye acts as an efficient quantum detector of photons. The spurious astronomical argument that the eye’s peak sensitivity is matched to the peak solar flux results directly from the inappropriate use of wavelength instead of frequency.

[FB20.04] General Education Physics: Light and Matter for Science and Non-Science Majors

Converting a high-enrollment general education physics course with no science majors to a first-year seminar has attracted, to my surprise, a different clientele: students with strong physics and mathematics backgrounds, most planning to major in a science. The theme in both cases is our deepening understanding of light and matter in the 19th and 20th centuries. However, my goals have been adjusted from a course for people who will likely not take more physics to a seminar aimed at developing perspectives students will not necessarily see in other science courses. How this has evolved the last three years will be described.

Reference: John K. Pribram, Light and Matter for Liberal Arts Students, AAPT Announcer, Vol 24, No. 2, p. 71 (1994).

[FB20.05] How To Teach Flight

The physical mechanisms of flight, as taught by the airfoil/Bernoulli canon, have not been well-transferred to students or the lay public. As a result, many people sense an element of magic as the airplane in which they ride lifts off the ground. Otherwise competent scientists make statements (perhaps in jest) that it should be impossible for bumblebees to fly.

This lack of understanding, of something so pervasive in everyday life, has implications for scientific literacy, the widespread acceptance of pseudo-science by the lay public, and public support for scientific research.

We will present an approach that should give students a better, intuitive understanding of flight and even motions of bodies in other fluids (e.g., sailing, water-skiing, fish pro- pulsion). We concentrate on the Newtonian reaction forces and focus attention on the mass of fluid striking the moving body, tentatively calling it the Transient Reactive Inertial Mass (TRIM).

In this approach, it is the TRIM that holds the airplane up in the air; that the keel of a sailboat or the bumblebee wing pushes against. The forces acting on an object moving in an invisible fluid become intuitively obvious to the student.

[FB20.06] Plectra, Spectra, and Mathematical Models

I examine how the stiffness of plectra (small pieces of material that pluck a string) affect the spectra of the sound from a harpsichord string. To do this, I vary the stiffness of the plectra by shaping them with a hobby knife and using different kinds of material. I measure the spectra with a band pass filter. I also measure the height at which the stirng is dropped when plucked. With that information, I am able to construct a mathematical model of a plucked ideal string for comparison. I briefly explore the link between these considerations and the timbre of the instrument.

[FB20.07] Revisiting the PASCO Smart Pulley Atwood's Machine

The PASCO Smart Pulley begs to be used as an Atwood's machine, but even its small moment of inertia and friction degrade calculated values of "g" to unacceptably low values when small mass differences are used. A simple theoretical model which includes the inertia and friction effects is developed. This model is tested experimentally to determine its validity. Consistent values for "g," the moment of inertia of the pulley, and the effective friction are found using this method.

[FB20.08] Car moving at constant speed; force of roadway on tires is forward? backward?

Push forward on the trunk lid. At slow speed, force of roadway on tires is backward. Let engine do the work. Force of roadway on drive-wheel tire is forward. Force of roadway on non-drive-wheel tire is backward. Paradox? No. The tire deformation is different. Front-wheel-drive cars are lengthened by driving; rear-wheel-drive cars are compressed. But show me the physics textbook that tells you these obvious consequences of Newton’s Laws!

[FB20.09] A Bucky Ball Model of the Earth

A bucky ball model of the Earth is presented. The areas of the 12 pentagons and 20 hexagons are calculated and their positions on the globe determined. Curiously, most continents fit quite well into a pentagon or/and a hexagon. The Arctic Ocean and Antarctica are situated on pentagons centered around the north and south poles respectively. North America straddles over a hexagon in the northern hemisphere whereas South America is situated on a hexagon which lies three-quarters in the southern hemisphere. Australia, when moved 15 degrees westward longitudinally, lies inside a pentagon in the southern hemisphere. Africa is represented by a hexagon plus an adjacent pentagon after it is moved 15 degrees eastward longitudinally and rotated 22 degrees in the clockwise direction. Only Eurasia does not fit easily into this scheme.

[FB20.10] Comprehensive Anthropometry of Pediatric Subjects for Dynamic Events

The response of human subjects to high-severity insults has traditionally been studied with various approaches, including the use of mechanical and analytical surrogates. Much of this effort has been centered on a limited number of surrogates, such as a fiftieth-percentile adult male and other standard choices. One reason why infants have not been considered to the same extent is the considerable difficulty in obtaining reliable and consistent data for young subjects. A meticulous system for measuring children less than two years old has been developed during this research to overcome these problems. The rationale for determining which data should be captured, and how they should be captured, is discussed. Subsequent analyses complete the rigorous protocol by producing physical parameters for a complex multi-segmented surrogate, with precise values for segment mass, dimensions, and moments of inertia. The success of the approach described here is emphasized with important practical examples.

[FB20.11] Physics as a Key Element in the Complete Description of Dichotomies in Injury Distribution

A series of related studies has shown why a comprehensive grasp of physics is essential for an accurate appraisal of injury. Such use of physics is particularly valuable when considering a multiplicity of possible injury sites within the same subject. A nominally straightforwaard case is presented in this paper to demonstrate how a detailed application of physics enables one to explain apparently counter-intuitive findings from a clinical examination and the physical evidence: (a) injury observed in a lower extremity, but absent in the main body; (b) injury observed on one side of the body, but not on the other; and (c) injury consistent with one end of the range of known impact severity, but not with the other end just a small amount lower. This research was successful because all potentially significant physical parameters, such as height, weight, and gender, were included in the analysis of injury mechanisms. 1. S.J. Shaibani, "The Physics of Injury Causation and Mitigation in Blunt Chest Trauma," Announcer 26 (4), 42 (1996). 2. S.J. Shaibani, "Catastrophic Increase in Barrier Stiffness," Bull. Am. Phys. Soc. 42, 2289 (1997). 3. S.J. Shaibani, "Proper Treatment of Complex Human Structures," Announcer 27 (4), 100 (1997). 4. S.J. Shaibani, "The Importance of Physics in Medicine -- A Pedagogical Challenge," Announcer 28 (4), 103 (1998).

Part F of program listing