"The harmonic oscillator propagator," Barry R. Holstein,
Am. J. Phys. 66, 583 (1998)
The Feynman propagator for the harmonic oscillator is evaluated by a variety of path-integral-based means
"Circular orbits inside the sphere of death," Kirk T. McDonald, Am. J. Phys. 66, 419 (1998)
A wheel or sphere rolling without slipping on the inside of a sphere in a uniform gravitational field can have stable circular orbits that lie wholly above the "equator," while a particle sliding freely cannot.
"What is quantum mechanics trying to tell us?," N. David Mermin, Am. J. Phys. 66, 753 (1998)
I explore whether it is possible to make sense of the quantum mechanical description of physical reality by taking the proper subject of physics to be correlation and only correlation, and by separating the problem of understanding the nature of quantum mechanics from the hard problem of understanding the nature of objective probability in individual systems, and the even harder problem of understanding the nature of conscious awareness. The resulting perspective on quantum mechanics is supported by some elementary but insufficiently emphasized theorems. Whether or not it is adequate as a new Weltanschauung, this point of view toward quantum mechanics provides a different perspective form which to teach the subject or
"The sweet spot of a baseball bat," Rod Cross, Am. J. Phys. 66, 772 (1998)
The sweet spot of a baseball bat, like that of a tennis racket, can be defined either in terms of a vibration node or a centre of percussion. In order to determine how each of the sweet spots influences the “feel” of the bat, measurements were made of the impact forces transmitted to the hands. Measurements of the bat velocity, and results for a freely suspended bat, were also obtained in order to assist in the interpretation of the force waveforms. The results show that both sweet spots contribute to the formation of a sweet spot zone where the impact forces on the hands are minimized. The free bat results are also of interest since they provided particularly elegant examples of wave excitation and propagation, suitable for a student demonstration or experiment.
"Introducing quantum mechanics: One-particle interferences," Valerio Scarani and Antoine Suarez, Am. J. Phys. 66, 718 (1998)
One-particle quantum interference is presented using probably the simplest setup. This review of experimental facts may be useful as a short self-contained introduction to quantum mechanics, highlighting the dependence of interference on indistinguishability.
"Do cathedral glasses flow?" Edgar Dutra Zanotto. Am. J. Phys. 66, 392 (1998)
A general belief among members of the scientific community is that glass articles can be bent irreversibly and that they flow at ambient temperature. This myth is mostly based on widespread stories that stained-glass windows of medieval cathedrals are thicker in the lower parts. In this paper I estimate the time periods required for glass to flow and deform at ordinary temperatures, using calculated viscosity curves for several modern and ancient glass compositions. The conclusion is that window glasses may flow at ambient temperature only over incredibly long times, which exceed the limits of human history.
"Causality and negative group delays in a simple band pass amplifier," Morgan W. Mitchell and Raymond Y. Chiao, Am. J. Phys. 66, 14 (1998)
We demonstrate a bandpass amplifier which can be constructed from common electronic components and has the surprising property that the group delay is negative in most spectral regions. A pulse propagating through a chain of such amplifiers is advanced by several milliseconds: the output waveform precedes the input waveform. Although striking, this behavior is not in conflict with causality, as demonstrated by experiments with pulses which start or end abruptly.
"Materials physics: A new contemporary undergraduate laboratory," Herbert Jaeger, Michael J. Pechan and Daniel K. Lottis, Am. J. Phys. 66, 724 (1998)
We have developed a laboratory course focusing on the physics of materials. This course, taught in place of a "conventional" lecture-only solid state or condensed matter physics course, helps prepare students for the technical work force and also serves as a solid, broad-based foundation for students bound for graduate school. In addition, the course illustrates the increasingly interdisciplinary nature of physics. Classroom activities and experiments concentrate on four materials classes: metals, ceramics, semiconductors, and polymers. Experiments include electrical conductivity of metals and semiconductors; ionic conductivity of ceramics; superconductivity in metals, alloys and ceramics; preparation and characterizations of metallic thin films; scanning tunneling microscopy; magnetic properties of materials; impedance spectroscopy of solid electrolytes; phase diagram determination by differential thermal analysis and x-ray diffractometry; Hall effect in pure and doped semiconductors; dielectric response of polymers; and mechanical properties of polymers.
"Who were Fabry and Perot?" Joseph F. Mulligan, Am. J. Phys. 66, 797 (1998)
IN 1897 Charles Fabry and Alfred Perot published their most important article on what we now call the Fabry-Perot interferometer. Despite the great importance of this instrument for present-day research in physics and astrophysics, its inventors are almost completely unknown to most physicists. This article presents brief accounts of the life and work of Fabry and Perot, who at the beginning of the twentieth century were highly regarded by physicists throughout the world for their contributions to astrophysics, including Fabry's 1913 discovery (with Henri Buisson) of the ozone layer in the Earth's atmosphere.
"Approximate trajectories for projectile motion with air resistance," Michael A. B. Deakin and G. J. Troup, Am. J. Phys. 66, 34 (1998)
To remarkable accuracy and under a wide variety of conditions, the trajectories of projectiles under various laws of resistance may be approximated by cubic curves. This allows for the relatively simple calculation of many details of the flight
"Quantum measurement theory and the Stern-Gerlach experiment," M. Hannout, S. Hoyt, A. Kryowonos and A. Widom, Am. J. Phys. 66, 377 (1998)
The Stern-Gerlach experiment was one of the early illustrative examples of the Bohr view of quantum mechanics. In the Bohr view, a measurement is an interaction between a quantum object and an apparatus which acts in classical fashion. There are still open problems with this concept many of which enter into the discussion of the original Stern-Gerlach measurement.
* Each article can be accessed from any OSU computer by clicking on link at start of each abstract and then searching for listed article.