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Feb 2006

Volume 74, Issue 2, pp. 93-167

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Do not forget to teach about the scientific method

Michael C. LoPresto

American Journal of Physics -- February 2006 -- Volume 74, Issue 2, pp. 93

Online Publication Date: Jan 2006

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Abstract Unavailable
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01.40.Di Course design and evaluation
95.00.00 Fundamental astronomy and astrophysics; instrumentation, techniques, and astronomical observations

Student knowledge of physics history

Jay M. Pasachoff

American Journal of Physics -- February 2006 -- Volume 74, Issue 2, pp. 93

Online Publication Date: Jan 2006

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01.65.+g History of science
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Syringe thermodynamics: The many uses of a glass syringe

David P. Jackson and Priscilla W. Laws

American Journal of Physics -- February 2006 -- Volume 74, Issue 2, pp. 94 | Cited 2 times

Online Publication Date: Jan 2006

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Glass syringes have precision fit low-friction pistons and are relatively inexpensive, which makes them an ideal tool for studying the thermal behavior of gases. The glass syringe is used to construct a thermometer, a miniature hydraulic press, and a working heat engine. Concepts illuminated by these experiments include temperature, pressure, the ideal gas law, work, internal energy, and the first law of thermodynamics.
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01.50.Pa Laboratory experiments and apparatus

The indirect measurement of biomechanical forces in the moving human body

Melanie Cluss, Kenneth Laws, Natalie Martin, T. Scott Nowicki, and Allan Mira

American Journal of Physics -- February 2006 -- Volume 74, Issue 2, pp. 102 | Cited 4 times

Online Publication Date: Jan 2006

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Inexpensive experimental techniques now exist for indirectly measuring forces within the moving human body. These techniques involve nontrivial applications of basic physical principles, have practical uses, and are appropriate for undergraduate experimentation. A two-dimensional video motion analysis is used to find the accelerations of various parts of the body, and anatomical geometry is used to determine specific biomechanical forces and torques. The simple movement of a dancer landing from a vertical jump is analyzed through the use of a theoretical model of the leg to find the forces in the tendons attached to the knee. It is shown that these forces can be sufficiently large to lead to injury if jumps are performed repetitively.
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47.00.00 Fluid dynamics
87.00.00 Biological and medical physics

Quantum mechanics of the 1∕x2 potential

Andrew M. Essin and David J. Griffiths

American Journal of Physics -- February 2006 -- Volume 74, Issue 2, pp. 109 | Cited 16 times

Online Publication Date: Jan 2006

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In quantum mechanics a localized attractive potential typically supports a (possibly infinite) set of bound states, characterized by a discrete spectrum of allowed energies, together with a continuum of scattering states, characterized (in one dimension) by an energy-dependent phase shift. The 1∕x2 potential on 0<x<∞ confounds all of our intuitions and expectations. Resolving its paradoxes requires sophisticated theoretical machinery: regularization, renormalization, anomalous symmetry-breaking, and self-adjoint extensions. Our goal is to introduce the essential ideas at a level accessible to advanced undergraduates.
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03.65.-w Quantum mechanics

Reducing the gender gap in the physics classroom

Mercedes Lorenzo, Catherine H. Crouch, and Eric Mazur

American Journal of Physics -- February 2006 -- Volume 74, Issue 2, pp. 118 | Cited 15 times

Online Publication Date: Jan 2006

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We investigate if the gender gap in conceptual understanding in an introductory university physics course can be reduced by using interactive engagement methods that promote in-class interaction, reduce competition, foster collaboration, and emphasize conceptual understanding. To this end we analyzed data from the introductory calculus-based physics course for non-majors at Harvard University taught traditionally or using different degrees of interactive engagement. Our results show that teaching with certain interactive strategies not only yields significantly increased understanding for both males and females, but also reduces the gender gap. In the most interactively taught courses, the pre-instruction gender gap was gone by the end of the semester.
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01.40.Fk Research in physics education

Teaching the principles of statistical dynamics

Kingshuk Ghosh, Ken A. Dill, Mandar M. Inamdar, Effrosyni Seitaridou, and Rob Phillips

American Journal of Physics -- February 2006 -- Volume 74, Issue 2, pp. 123 | Cited 13 times

Online Publication Date: Jan 2006

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We describe a simple framework for teaching the principles that underlie the dynamical laws of transport: Fick’s law of diffusion, Fourier’s law of heat flow, the Newtonian viscosity law, and the mass-action laws of chemical kinetics. In analogy with the way that the maximization of entropy over microstates leads to the Boltzmann distribution and predictions about equilibria, maximizing a quantity that E. T. Jaynes called “caliber” over all the possible microtrajectories leads to these dynamical laws. The principle of maximum caliber also leads to dynamical distribution functions that characterize the relative probabilities of different microtrajectories. A great source of recent interest in statistical dynamics has resulted from a new generation of single-particle and single-molecule experiments that make it possible to observe dynamics one trajectory at a time.
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05.40.-a Fluctuation phenomena, random processes, noise, and Brownian motion
05.60.-k Transport processes

Carnot and the fields formulation of elementary thermodynamics

J. H. Hannay

American Journal of Physics -- February 2006 -- Volume 74, Issue 2, pp. 134 | Cited 1 time

Online Publication Date: Jan 2006

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Thermodynamics centers on the fact that work and heat are not functions of state. However, the natural formalism to capture this fact was not incorporated into thermodynamics because it was formulated before the development of vector field notation. One reason for reexamining this omission is provided by the work of Sadi Carnot that initiated thermodynamics. His results, which he derived from his grand principle, were not obtained by what is now called the 2nd law of thermodynamics or by the 1st law of thermodynamics. Instead they were obtained by a (co)vector formula, albeit expressed in words not symbols. Carnot’s formula allowed him to obtain several standard results of thermodynamics, including the Clausius-Clapeyron equation. The formula also implies the Maxwell relations.
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05.70.-a Thermodynamics

Helicity conservation under Reidemeister moves

Elizabeth L. Bouzarth and Hans Pfister

American Journal of Physics -- February 2006 -- Volume 74, Issue 2, pp. 141

Online Publication Date: Jan 2006

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We discuss a connection between two fields that appear to have little in common: plasma physics and mathematical knot theory. Plasma physicists are interested in studying helicity conservation in magnetic flux ropes and knot theorists commonly consider “Reidemeister moves,” transformations that preserve a property called “knottedness.” To study the tangling, twisting, and untwisting of magnetic flux ropes, it is helpful to know which topological transformations conserve helicity. Although the second and third types of Reidemeister moves applied to a magnetic flux rope clearly conserve the helicity of the flux rope, the first type of Reidemeister move appears to be in conflict with helicity conservation. We show that all three Reidemeister moves conserve helicity in magnetic flux ropes.
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02.00.00 Mathematical methods in physics
50.00.00 PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES

Experimentally probing the shape of extra dimensions

Marc Sher and Kelly A. Sullivan

American Journal of Physics -- February 2006 -- Volume 74, Issue 2, pp. 145

Online Publication Date: Jan 2006

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Theories with compact extra dimensions have become increasingly popular. In some theories the standard model particles are confined to our four-dimensional world and only gravity can propagate in the extra dimensions. In these models the size of the extra dimensions can be as large as hundreds of microns. The functional dependence of the gravitational force on distance is well known at both large and small distances compared to the size of the extra dimensions; for two extra dimensions, for example, it varies from 1∕r2 to 1∕r4 as the distance decreases. However, the dependence for intermediate distances has not been fully calculated. We determine this dependence as a function of both the size of the extra dimensions and the possible angle between the extra dimensional unit vectors and show that high precision measurements of the gravitational force would make possible the determination of the shape of the extra dimensions.
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04.00.00 General relativity and gravitation

Generalization of the Schott energy in electrodynamic radiation theory

José A. Heras and R. F. O’Connell

American Journal of Physics -- February 2006 -- Volume 74, Issue 2, pp. 150 | Cited 7 times

Online Publication Date: Jan 2006

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We discuss the origin of the Schott energy in the Abraham-Lorentz version of electrodynamic radiation theory and how it can be used to explain some apparent paradoxes. We also derive the generalization of this quantity for the Ford-O’Connell equation, which has the merit of being derived exactly from a microscopic Hamiltonian for an electron with structure and has been shown to be free of the problems associated with the Abraham-Lorentz theory. We emphasize that the instantaneous power supplied by the applied force not only gives rise to radiation (acceleration fields), but it can change the kinetic energy of the electron and change the Schott energy of the velocity fields. The important role played by boundary conditions is noted.
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41.00.00 Electromagnetism; electron and ion optics

The radiation of a uniformly accelerated charge is beyond the horizon: A simple derivation

Camila de Almeida and Alberto Saa

American Journal of Physics -- February 2006 -- Volume 74, Issue 2, pp. 154 | Cited 5 times

Online Publication Date: Jan 2006

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By exploring some elementary consequences of the covariance of Maxwell’s equations under general coordinate transformations, we show that even though inertial observers can detect electromagnetic radiation emitted from a uniformly accelerated charge, comoving observers will see only a static electric field. This analysis can add insight into one of the most celebrated paradoxes of the last century.
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03.30.+p Special relativity
41.00.00 Electromagnetism; electron and ion optics
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Comment on “The distribution of composite measurements: How to be certain of the uncertainties in what we measure,” by M. P. Silverman, W. Strange, and T. C. Lipscombe [Am. J. Phys. 72 (8), 1068–1081 (2004)]

Robert D. Cousins and Frederick James

American Journal of Physics -- February 2006 -- Volume 74, Issue 2, pp. 159 | Cited 1 time

Online Publication Date: Jan 2006

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Abstract Unavailable
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06.00.00 Metrology, measurements, and laboratory procedures

Erratum: “Max Born and the quantum theory” [Am. J. Phys. 73 (11), 999–1008 (2005)]

Jeremy Bernstein

American Journal of Physics -- February 2006 -- Volume 74, Issue 2, pp. 160

Online Publication Date: Jan 2006

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99.10.-x Errata and other corrections
01.60.+q Biographies, tributes, personal notes, and obituaries
01.65.+g History of science
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A compact apparatus for muon lifetime measurement and time dilation demonstration in the undergraduate laboratory

Thomas Coan, Tiankuan Liu, and Jingbo Ye

American Journal of Physics -- February 2006 -- Volume 74, Issue 2, pp. 161 | Cited 3 times

Online Publication Date: Jan 2006

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We describe a compact apparatus for measuring the charge-averaged lifetime of atmospheric muons in plastic scintillator using low-cost, low-power electronics. We present measurements of the stopping rate of atmospheric muons as a function of altitude to demonstrate relativistic time dilation. The apparatus is designed for the advanced undergraduate physics laboratory and is suitable for field measurements.
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01.50.Pa Laboratory experiments and apparatus
03.30.+p Special relativity
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Post-Use Review. Physics for Scientists and Engineers: A Strategic Approach, with Mastering Physics

Randall D. Knight and Kieran Mullen, Reviewer

American Journal of Physics -- February 2006 -- Volume 74, Issue 2, pp. 165

Online Publication Date: Jan 2006

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Abstract Unavailable
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01.55.+b General physics
01.30.Vv Book reviews

“Astrobiology: A Multidisciplinary Approach”

Jonathan I. Lunine and John Armstrong, Reviewer

American Journal of Physics -- February 2006 -- Volume 74, Issue 2, pp. 167

Online Publication Date: Jan 2006

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Abstract Unavailable
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87.00.00 Biological and medical physics
95.00.00 Fundamental astronomy and astrophysics; instrumentation, techniques, and astronomical observations
01.30.Vv Book reviews
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