Volume 47, Issue 1, January 1979
 Papers


American Association of Physics Teachers 1978 Robert A. Millikan Lecture Award to Alfred Bork
View Description Hide Description 
Interactive learning: Millikan Lecture, American Association of Physics Teachers, London, Ontario, June, 1978
View Description Hide Description 
Quark physics without quarks: A review of recent developments in S‐matrix theory
View Description Hide DescriptionA review is given of the developments in S‐matrix theory over the past five years which have made it possible to derive results characteristic of quark models without any need to postulate the existence of physical quarks. In the new approach, the quark patterns emerge as a consequence of combining the general S‐matrix principles with the additional concept of order.

Physics for architects
View Description Hide DescriptionWe describe a program which was prompted by and designed to satisfy the modern needs of architects who will be confronted more and more with the constraints imposed by the principles of physics, particularly those relating to energy. The program is designed to make clear, through lectures and laboratory investigations, the relationship between concepts in physics and practice in architecture. It is designed to help the student of architecture recognize that the behavior of a structure is as much a part of his creativity as the structure itself. Experiments range from individual labortory experiments to group around‐the‐campus experiments.

Some psychoacoustical experiments with all‐pass networks
View Description Hide DescriptionIt is shown how all‐pass filter sytems can be used in labortory experiments in the physics and psychophysics of sound and music. Particular applications include studies of the following: (i) lateralization of sounds in headphone listening; (ii) the spectral modifications produced by phasers, compared with admixing a time‐delayed signal; (iii) the pitch that can be obtained by dichotic processing of two spectrally flat noise signals, Huggins effect; and (iv) the perception of the dephasing of harmonics in complex tone. Some of the effects obtained from experiments on lateralization and on the Huggins effect appear to be new results.

Some remarks on the extended Galilean transformation
View Description Hide DescriptionThe Galilean transformation carries one inertial frame into another with a different velocity. The extended Galilean transformation carries an inertial frame into a rigid frame with uniform spatial, but arbitrary translational acceleration x′=x+ξ (t). Besides being useful in discussing the equivalence principle, this transformation provides a physical interpretation for the theorem in nonrelativistic quantum mechanics, that we cannot coherently combine states of different mass. This restriction comes about because we cannot distinguish between coordinate and proper time in nonrelativistic physics.

Comparison of classical and quantum mechanical uncertainties
View Description Hide DescriptionA comparison of classical and quantum uncertainties is presented for the particle‐in‐a‐box, the harmonic oscillator, and the one‐electron atom. It is found that the quantum results reduce to the classical in the limit of either very large quantum numbers or h→0. A classical uncertainty principle is derived and compared with its quantum analogue. A possible relationship between zero‐point motion and the uncertainty principle is noted.

Measurement oriented basic physics laboratory
View Description Hide DescriptionPhysical Measurements 1 is a measurement oriented basic physics laboratory course required of all sophomore students at the Colorado School of Mines. The course is intended to introduce students to the principles of measurement theory at a higher level than is common in an elementary physics lab. The subjects of error analysis, graphing, least‐squares analysis, experimental design, measuring instruments, and report writing are covered in a 1‐h/week lecture session. Experiments from mechanics and electricity and magnetism, that illustrate equally the principles of measurement theory and the principles of physics, are performed in 2‐h/week laboratory sessions. A workbook entitled C o n c e p t s o f P h y s i c a l M e a s u r e m e n t serves both as a textbook in measurement theory and a laboratory notebook.

Simplified relativistic force transformation equation
View Description Hide DescriptionA simplified relativistic force transformation equation is derived and then used to obtain the equation for the electromagnetic force on a charged particle, calculate the electromagnetic fields due to a point charge with constant velocity, transform electromagnetic fields in general, derive the Biot‐Savart law, and show that the constant of proportionality in Coulomb’s law is equal to the speed of light squared times the constant of proportionality in the Biot‐Savart law. All is done with simple vector algebra without using four vectors, tensors, or Maxwell’sequations. The simplification results from the fact that when one takes the usual force transformation law: F′=A (U)F, and rewrites it using the inverse transformation matrix, as F=A ^{−1}(U)F′, the resulting expression is more simple because A ^{−1}(U) is linear in the velocity, U but A (U) is not.

Grundfagligt Speciale: An advanced laboratory‐research course for nonphysicists taught by physicists
View Description Hide DescriptionThe pedagogical and research advantages of an advanced laboratory‐research course for nonphysicists taught by physicists are discussed. The practical considerations which determine the structure and content of such a course are emphasized with particular attention given to those features which would be most helpful to others contemplating a similar course. A successful example of such a course developed by the authors is discussed in detail.

Topological solitons in physics
View Description Hide DescriptionWe present an introduction to topological solitons. A broad definition of solitons and a discussion of their role in physics is given. To illustrate this concept, we describe in some detail vortices and magnetic monopoles which are examples of topological solitons in two and three spatial dimensions.

Application of the parabolic approximation to predict acoustical propagation in the ocean
View Description Hide DescriptionA simplified derivation of the parabolic approximation to the acoustical wave equation is presented. Exact solutions to this approximate equation are compared with solutions to the wave equation to demonstrate the applicability of this method to the study of underwater sound propagation. A technique for solving the parabolic equation is presented, and transmission loss predicted by this method is compared with experimental results for sound propagation in a coastal environment.

Experimental determination of the mass of air molecules from the law of atmospheres
View Description Hide DescriptionA sensitive gas pressure gauge has been constructed for use in a student experiment involving the law of atmospheres. From pressure data obtained at selected elevations the average mass of air molecules is determined and then compared with the average mass as calculated from the molecular weights and percentages by volume of the major gaseous constituents of the air.

Laboratory study of airborne fallout particles and their time distribution
View Description Hide DescriptionSimple γ‐ray detection and analysis techniques were utilized to study the radioactivity in samples of filtered airborne particulate, collected daily for approximately the first month after the 18 September 1977 Chinese nuclear detonation. Fourteen fission products were detected in the filter samples which contained radioactive fallout, and fluctuations in the daily fallout activity levels suggested a global fallout orbit time of approximately 20 days.

Monte Carlo calculation as an aid in teaching solid‐state diffusion
View Description Hide DescriptionA simple Monte Carlo method is used to simulate an atomistic model of solid‐state diffusion. This approach illustrates some of the principles of diffusion and in particular verifies a solution to Fick’s second law. The role and calculation of the diffusion correlation factor is also discussed.

Brachistochrones, tautochrones, evolutes, and tesselations
View Description Hide DescriptionThe force fields of uniform gravity and of gravity inside a spherical body of uniform density were previously known to possess the property that the brachistochrone and the tautochrone are identical (cycloid and hypocycloid, respectively,). It is shown that centrifugal force in a rotating reference frame possesses the same property. In a plane normal to the axis of rotation the brachistochrone tautochrone is the epicycloid. The evolutes of hypocycloid and epicycloid are found. The figures of cycloid, hypocycloid, and epicycloid each with its evolute are shown to produce tesselations of the plane. In a plane including the axis of rotation the rotating reference frame has other brachistochrones and tautochrones which are not identical.

Semiclassical quantization of the electron‐dipole system
View Description Hide DescriptionA recent note by Fox called attention to a semiclassical treatment by Fermi in 1925 of the motion of an electron in the field of two stationary positive charges. The similarity of this problem to that of an electron moving in a dipole field prompted the author to investigate the latter system under semiclassical quantization. It is shown that Bohr quantization leads to the value D _{min} = (3√3/4) e a _{0}=1.30e a _{0} for the minimum dipole moment required to bind an electron. The implied separation of unit dipole charges is identical with a special value for unit positive‐charge separation given by Fermi. Furthermore, this semiclassical value of D _{min} is more than twice the quantum‐mechanical value D _{min}=0.639e a _{0}.

Effect of weight transfer on a vehicle’s stopping distance
View Description Hide DescriptionAs a braking vehicle decelerates, friction forces between the tires and road produce a torque about the vehicle’s center of mass. This effect, called weight transfer, removes weight from the rear wheels and results in a minimum stopping distance that is in general longer than that given in the usual textbook treatment. In this paper we present an analysis of the minimum stopping distance problem taking into account the effect of weight transfer on (i) nonskidding vehicles and (ii) front‐ or rear‐wheels‐skidding vehicles. Expressions for the minimum stopping distances are given for both cases in terms of vehicle geometry and the coefficients of friction. In the case of nonskidding stops we obtain an expression for the optimum brake ratio which will allow all wheels to simultaneously brake at the point of incipient skid. Under this condition a minimum ’’textbook’’ stop is achievable in principle, but only on a given road surface. These results are found to be in qualitative agreement with measured stopping distance data.

Approximate classical theory of scattering
View Description Hide DescriptionAn approximate method is developed for elasticscattering at large angle in the framework of classical mechanics. A simple formula for differential cross section is obtained. This formula which no longer involves any integrations provides a quick way of evaluating cross sections. Our method is illustrated through examples and is shown to work well.

A student’s experiment for the determination of the rest energy E _{0} of electrons
View Description Hide DescriptionElectrons in the energy range of several kilo‐electron‐volts reach velocities of approximately one tenth the speed of light. Though for t these electrons the relativistic mass increase is less than 1%, it affects the results of x‐ray photoelectron spectrometry(XPS) substantially. Thus a relativistic formalism allows the obtaining of the rest energy of electrons (E _{0}) as an experimental result of a series of XPS measurements.
