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Apr 1981

Volume 49, Issue 4, pp. 299-383

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Letter to the Editor

Theodore Bernstein

American Journal of Physics -- April 1981 -- Volume 49, Issue 4, pp. 299

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41.20.Cv Electrostatics; Poisson and Laplace equations, boundary-value problems
41.20.Gz Magnetostatics; magnetic shielding, magnetic induction, boundary-value problems

Letter to the Editor

James B. Lee

American Journal of Physics -- April 1981 -- Volume 49, Issue 4, pp. 299

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03.65.Ta Foundations of quantum mechanics; measurement theory
43.55.-n Architectural acoustics

Letter to the Editor

Steven B. Berger

American Journal of Physics -- April 1981 -- Volume 49, Issue 4, pp. 299

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01.90.+g Other topics of general interest (restricted to new topics in section 01)

Letter to the Editor

Robert Gordon

American Journal of Physics -- April 1981 -- Volume 49, Issue 4, pp. 300

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01.40.G- Curricula and evaluation
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Resource letter SP‐2: Symmetry and group theory in physics

Joe Rosen

American Journal of Physics -- April 1981 -- Volume 49, Issue 4, pp. 304 | Cited 2 times

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The author has selected material relevant to symmetry and group theory in physics. Entries are marked E (elementary), I (intermediate), and A (advanced) to designate their level. Articles selected for incorporation in a reprint volume (to be published seperately by the American Association of Physics Teachers) are marked with an asterisk().
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01.30.Rr Surveys and tutorial papers; resource letters
11.30.-j Symmetry and conservation laws
02.20.-a Group theory

Bow and arrow dynamics

W. C. Marlow

American Journal of Physics -- April 1981 -- Volume 49, Issue 4, pp. 320 | Cited 5 times

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Past analyses of bow and arrow dynamics have assumed the string to be inextensible. This results in predictions of efficiencies that are significantly higher than measured values (efficiencies over 90% are predicted versus 70% to 85% for measurements, circa 1960). The present analysis allows for an elastic string. It is found that arrow exit then takes place when the string and bow limbs still have substantial kinetic energy, and therefore this energy is unavailable for kinetic energy of the arrow. Moreover, the potential energy remaining in the string and bow limb system can also reduce the amount of energy available for the arrow. For the Hickman model of a long bow used in this study, the elastic string prediction of efficiency is 78%, whereas the inelastic prediction is 92%. The analysis utilizes a Lagrangian distributed mass formulation to develop the governing equations of motion and to generate an equivalent point mass model. The equations of motion were numerically integrated to obtain efficiency, arrow velocity, virtual masses, string tension, string extension, arrow exit time, string and limb potential energies, system momentum, and the dynamic force required to hold the bow handle stationary. Estimates of the effect of air resistance were made and found to be less than 2% of the total system energy. The vibratory dynamics of the string and bow limbs subsequent to arrow exit was analyzed. The results of the elastic string considerations are in reasonable agreement with experimental data and negate the usual explanation for the long‐standing discrepancy between theory and experiment as due to air resistance and hysteresis losses in the string and bow limbs.
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45.05.+x General theory of classical mechanics of discrete systems

Stability and oscillations of a soap film: An analytic treatment

Loyal Durand

American Journal of Physics -- April 1981 -- Volume 49, Issue 4, pp. 334 | Cited 1 time

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In this paper we consider the stability and oscillations (or small motions) of a soap film suspended between parallel coaxial rings. The problem of determining the equilibrium shape of such a film is a standard problem in the calculus of variations, and is often used to introduce variational methods in mechanics texts. However, the stability of the resulting surfaces is usually not discussed, and the small‐motion problem is not analyzed in any standard reference. We show that both the stability and small‐motion problem can be treated quite easily using eigenfunction methods familiar in elementary quantum mechanics. We use these methods to determine the range of parameters for which the solutions to the variational problem (the extremal surfaces) are stable, and analyze the small motions of the film (with examples) near both extremal and nonextremal surfaces.
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45.05.+x General theory of classical mechanics of discrete systems
03.65.-w Quantum mechanics

Augmenting course quality through the use of videotapes

Donald Shult

American Journal of Physics -- April 1981 -- Volume 49, Issue 4, pp. 344

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Several ways of easily producing and using videotapes to improve general physics classes have been developed. These take a minimum of equipment and have been shown to be highly successful.
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01.50.F- Audio and visual aids

Elementary derivation of the radiation field from an accelerated charge

Barry R. Holstein and Arthur R. Swift

American Journal of Physics -- April 1981 -- Volume 49, Issue 4, pp. 346

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Using only the equivalence principle and elementary electrodynamics we calculate the radiation from an accelerating charge in a direction perpendicular to its motion.
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01.40.-d Education
03.50.De Classical electromagnetism, Maxwell equations

Little group for photons and gauge transformations

D. Han and Y. S. Kim

American Journal of Physics -- April 1981 -- Volume 49, Issue 4, pp. 348 | Cited 14 times

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Based on Weinberg’s work on Lorentz‐transformation properties of massless particles, we discuss the little group for photons and gauge transformations from a pedagogical standpoint. It is pointed out that the ’’translational’’ degrees of freedom associated with the photon little group can generate a transformation which guarantees the transversality of the four‐vector representation for photons. This little‐group transformation, which leaves the photon momemtum invariant, can be regarded as a gauge transformation.
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01.40.-d Education
11.30.Cp Lorentz and Poincaré invariance

The Doppler demon

Jack Denur

American Journal of Physics -- April 1981 -- Volume 49, Issue 4, pp. 352 | Cited 1 time

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Equilibrium blackbody radiation, like all radiation, is, in general, Doppler shifted if it is emitted and/or reflected from a moving body. The relevance of this fact to the analysis of Maxwell’s demon, which has been previously neglected, is revealed in this paper. In particular, we find that, by appropriately taking advantage of this fact, Maxwell’s demon is, at least in principle, capable of operating, albeit very weakly, in violation of the Second Law of Thermodynamics.
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05.70.-a Thermodynamics

Physics of basketball

Peter J. Brancazio

American Journal of Physics -- April 1981 -- Volume 49, Issue 4, pp. 356 | Cited 4 times

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Does a knowledge of physics help to improve one’s basketball skills? Several applications of physical principles to the game of basketball are examined. The kinematics of a basketball shot is studied, and criteria are established for determining the best shooting angle at any given distance from the basket. It is found that there is an optimum shooting angle which requires the smallest launching force and provides the greatest margin for error. Some simple classroom illustrations of Newtonian mechanics based on basketball are also suggested.
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01.55.+b General physics
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Abraham–Minkowski controversy in static fields: An example

H. M. Lai

American Journal of Physics -- April 1981 -- Volume 49, Issue 4, pp. 366 | Cited 3 times

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41.20.Cv Electrostatics; Poisson and Laplace equations, boundary-value problems
41.20.Gz Magnetostatics; magnetic shielding, magnetic induction, boundary-value problems

Drag force exerted by water on the human body

A. Bellemans

American Journal of Physics -- April 1981 -- Volume 49, Issue 4, pp. 367

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87.19.rs Movement
87.19.ru Locomotion

Comment on ’’The problem of being a normal deviate’’

Frank Munley

American Journal of Physics -- April 1981 -- Volume 49, Issue 4, pp. 368

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45.05.+x General theory of classical mechanics of discrete systems

Space‐time diagrams with base vectors

C. Leubner

American Journal of Physics -- April 1981 -- Volume 49, Issue 4, pp. 368 | Cited 1 time

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03.30.+p Special relativity

Reduced matrix elements

B. R. Judd

American Journal of Physics -- April 1981 -- Volume 49, Issue 4, pp. 371 | Cited 1 time

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03.65.-w Quantum mechanics

Cancellation of internal forces

R. Chen

American Journal of Physics -- April 1981 -- Volume 49, Issue 4, pp. 372

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45.05.+x General theory of classical mechanics of discrete systems

Erratum: ’’A density of states‐frequency theorem for general one‐dimensional oscillator systems’’ [Am. J. Phys. 48, 458(1980)]

J. P. McKelvey

American Journal of Physics -- April 1981 -- Volume 49, Issue 4, pp. 373

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03.65.-w Quantum mechanics
45.05.+x General theory of classical mechanics of discrete systems
99.10.Cd Errata

Erratum: ’’Is the isotropy of the speed of light a convention?’’ [Am. J. Phys. 48, 654(1980)]

Shing‐Fai Fung and K. C. Hsieh

American Journal of Physics -- April 1981 -- Volume 49, Issue 4, pp. 373

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03.30.+p Special relativity
06.20.Jr Determination of fundamental constants
99.10.Cd Errata
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Intelligent light bulb: A negative feedback demonstration

R. L. T. Wolfson

American Journal of Physics -- April 1981 -- Volume 49, Issue 4, pp. 374

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The author demonstrates the Intelligent Light Bulb, an optoelectronic feedback circuit. The circuit is extremely simple and may be understood easily in dc terms. (AIP)
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01.50.My Demonstration experiments and apparatus

Wave demonstration device

Glen T. Clayton, Harry D. Downing, and Thomas O. Callaway

American Journal of Physics -- April 1981 -- Volume 49, Issue 4, pp. 375 | Cited 2 times

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01.50.My Demonstration experiments and apparatus
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Electricity in the 17th and 18th Centuries: A study of Early Modern Physics

J. L. Heilbron, Author and Samuel Devons

American Journal of Physics -- April 1981 -- Volume 49, Issue 4, pp. 376

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01.30.Ee Monographs and collections
01.65.+g History of science
03.50.De Classical electromagnetism, Maxwell equations

From Atoms to Quarks: An Introduction to the Strange World of Particle Physics

James S. Trefil and Robert H. Romer, Reviewer

American Journal of Physics -- April 1981 -- Volume 49, Issue 4, pp. 380

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01.30.Vv Book reviews

The Particle Play: An Account of the Ultimate Constituents of Matter

J. C. Polkinghorne and Robert H. Romer, Reviewer

American Journal of Physics -- April 1981 -- Volume 49, Issue 4, pp. 380

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01.30.Vv Book reviews

What Is the World Made Of? Atoms, Leptons, Quarks, and Other Tantalizing Particles

Gerald Feinberg and Robert H. Romer, Reviewer

American Journal of Physics -- April 1981 -- Volume 49, Issue 4, pp. 380

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01.30.Vv Book reviews

The Forces of Nature

P. C. W. Davies and Robert H. Romer, Reviewer

American Journal of Physics -- April 1981 -- Volume 49, Issue 4, pp. 380

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01.30.Vv Book reviews

Particles and Fields: Readings from Scientific American

William J. Kaufmann, III and Robert H. Romer, Reviewer

American Journal of Physics -- April 1981 -- Volume 49, Issue 4, pp. 380

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01.30.Vv Book reviews

Elementary Particle Physics: An Introduction

David C. Cheng, Gerard K. O'Neill, and Robert H. Romer, Reviewer

American Journal of Physics -- April 1981 -- Volume 49, Issue 4, pp. 380

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01.30.Vv Book reviews

Surprises in Theoretical Physics

Rudolf Peierls, Author and David Thouless

American Journal of Physics -- April 1981 -- Volume 49, Issue 4, pp. 382

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Abstract Unavailable
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01.30.mm Textbooks for graduates and researchers
01.55.+b General physics

The Atom in the Hospital (film)

Handel Film Corporation Producer and William F. Schmid, Reviewer

American Journal of Physics -- April 1981 -- Volume 49, Issue 4, pp. 383

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01.50.F- Audio and visual aids
87.57.-s Medical imaging
87.63.-d Non-ionizing radiation equipment and techniques
87.85.Pq Biomedical imaging
87.53.-j Effects of ionizing radiation on biological systems

Accelerated Motion and Angle of Lean (film)

Peter Poulides, Producer, Van E. Neie, Producer, and Glenn A. Schmitz

American Journal of Physics -- April 1981 -- Volume 49, Issue 4, pp. 383

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Abstract Unavailable
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01.50.F- Audio and visual aids
45.05.+x General theory of classical mechanics of discrete systems
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