AAPT Logo
AJP Logo
 
   
 

BROWSE VOLUMES

Year Range: 
Search Issue | RSS Feeds RSS
Previous Issue

Dec 2006

Volume 74, Issue 12, pp. 1045-I17

back to top
RSS Feeds

An integrated approach to physics seminars for students

J. F. DiTusa

American Journal of Physics -- December 2006 -- Volume 74, Issue 12, pp. 1045

Online Publication Date: Nov 2006

Full Text: Read Online (HTML) | Download PDF

Abstract Unavailable
Show PACS
01.40.-d Education
back to top
RSS Feeds

Citations for the 2006 Robert A. Millikan Award and the Klopsteg Memorial Lecture

Richard Peterson, Past President, AAPT

American Journal of Physics -- December 2006 -- Volume 74, Issue 12, pp. 1047

Online Publication Date: Nov 2006

Full Text: Read Online (HTML) | Download PDF

Abstract Unavailable
Show PACS
01.10.-m Announcements, news, and organizational activities

Millikan Award Lecture, 2006: Physics For All

Art Hobson

American Journal of Physics -- December 2006 -- Volume 74, Issue 12, pp. 1048 | Cited 1 time

Online Publication Date: Nov 2006

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We physics teachers must broaden our focus from physics for physicists and other scientists to physics for all. The reason, as the American Association for the Advancement of Science puts it, is that “[w]ithout a scientifically literate population, the outlook for a better world is not promising.” Physics for all (including the first course for scientists) should be conceptual, not technical. It should describe the universe as we understand it today, including special and general relativity, quantum physics, modern cosmology, nuclear physics, the standard model of particles and interactions, and quantum fields. Many science writers have shown that this description is possible. It should emphasize the scientific process and include such societal topics as global warming, nuclear weapons, and pseudoscience, because citizens need to vote intelligently on such issues.
Show PACS
01.75.+m Science and society
back to top
RSS Feeds

Interferometric measurement of the resonant absorption and refractive index in rubidium gas

K. G. Libbrecht and M. W. Libbrecht

American Journal of Physics -- December 2006 -- Volume 74, Issue 12, pp. 1055 | Cited 4 times

Online Publication Date: Nov 2006

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We present a laboratory demonstration of the Kramers-Kronig relation between the resonant absorption and refractive index in rubidium gas. Our experiment uses a rubidium vapor cell in one arm of a simple Mach-Zehnder interferometer. As the laser frequency is scanned over an atomic resonance, the interferometer output is affected by variations of both the absorption and refractive index of the gas with frequency, all of which can be calculated in a straightforward manner. Changing the vapor density and interferometer phase produces a family of different output signals. The experiment was performed using a commercially available tunable diode laser system that was designed specifically for the undergraduate physics laboratory. As a teaching tool this experiment is reliable, fun, and instructive, while it also introduces the student to some sophisticated and fundamental physical concepts.
Show PACS
01.50.Pa Laboratory experiments and apparatus
47.00.00 Fluid dynamics
42.00.00 Optics

Correction for the radii of curvature for electron beam trajectories in CENCO’s e/m apparatus

John Howell

American Journal of Physics -- December 2006 -- Volume 74, Issue 12, pp. 1061

Online Publication Date: Nov 2006

Full Text: Read Online (HTML) | Download PDF

Show Abstract
An analysis of the motion of electrons in the Cenco e/m apparatus produces results that differ from those in Cenco’s operating instructions. As an electron’s speed increases in the apparatus, it is subjected to a uniform magnetic field B as well as a uniform electric field E. The B field affects the position as well as the angle at which the electron enters the E-free region. The net effect of the B field corresponds to a correction to the radius in the electron’s orbit that is approximately one-third the correction given by Cenco.
Show PACS
01.50.Pa Laboratory experiments and apparatus

Multiple-beam interference with coaxial cable analogs of optical arrays

Jeffrey A. Davis, Darren A. Miller, María del Mar Sánchez-López, and Joaquin Cos

American Journal of Physics -- December 2006 -- Volume 74, Issue 12, pp. 1066 | Cited 4 times

Online Publication Date: Nov 2006

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We study the interference properties of N coherent oscillators by using an equivalent radiofrequency coaxial cable electrical system consisting of N coaxial cables of different lengths, a 1×N splitter, and a N×1 coupler. The typical multiple-beam interference pattern is measured for several values of N as a function of the frequency. Unlike its optical counterpart, we have to consider the attenuation of the cables. The experimental curves agree well with theory and show the characteristics of multiple-beam interference. This approach represents an inexpensive way of experimentally investigating optical arrays.
Show PACS
42.00.00 Optics
84.30.-r Electronic circuits

The role of shock waves in expansion tube accelerators

G. Olson, Richard Peterson, B. Pulford, M. Seaberg, K. Stein, C. Stelter, and R. Weber

American Journal of Physics -- December 2006 -- Volume 74, Issue 12, pp. 1071 | Cited 2 times

Online Publication Date: Nov 2006

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Simulations are combined with laboratory measurements to show the important role of shock waves in a popular physics demonstration, the “ping pong cannon.” The simulation and measurements confirm a developing shock wave that reflects from the end of the closed tube and approaching ball and the eventual formation of a transient localized pressure build-up near the exit tape barrier. This 2 atm burst of pressure peaks within a few microseconds of the ball’s arrival, resulting from the combination of near ambient gas density and shock heating to about 1200 K. Pulsed schlieren images beyond the exit confirm the sequence of internally reflected shock waves and the intense, hot air pressure pulse that explosively removes the exit tape just prior to the ball arrival.
Show PACS
01.50.Pa Laboratory experiments and apparatus
47.00.00 Fluid dynamics

The New Studio format for instruction of introductory physics

C. M. Sorensen, A. D. Churukian, S. Maleki, and D. A. Zollman

American Journal of Physics -- December 2006 -- Volume 74, Issue 12, pp. 1077 | Cited 1 time

Online Publication Date: Nov 2006

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We have developed the New Studio format of instruction for improved conceptual learning while retaining problem-solving skill development in large, first-year physics courses. This format retains the large lecture, but combines traditional recitation and laboratory instruction. The New Studio format integrates simplified laboratories with assigned homework problems to integrate conceptual and problem-solving skills. The studio format combines 2 hours of lecture with 4 hours of studio each week. The studio is taught for 2 hours twice per week, and consists of up to 40 students working in groups of four at tables equipped with modern instructional technology and apparatus. The group setting allows for peer instruction and development of group skills. The combination of traditional lecture with the studio format enables a research-oriented physics department with a large service teaching load to implement research-based pedagogy. Student gains on the Force Concept Inventory were similar to other courses taught by interactive engagement methods.
Show PACS
01.40.Fk Research in physics education

The role of mediation in collisions and related analogs

E. Bashkansky and N. Netzer

American Journal of Physics -- December 2006 -- Volume 74, Issue 12, pp. 1083 | Cited 2 times

Online Publication Date: Nov 2006

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We analyze the problem of one-dimensional collisions between a target mass m and the incident mass M and a third object, the mediator. The concept of an optimal mediator that yields the most efficient energy transfer between the incident and target objects is introduced. A mediator consisting of a chain of colliding particles with masses that follow a geometric progression is considered. A paradox that arises when the number of particles in the chain goes to infinity is discussed. In this case a complete energy transfer from the incident to the target mass can be achieved for any mass ratio M∕m. The analogs of this problem in multilayer optics and quantum mechanics are also discussed.
Show PACS
47.00.00 Fluid dynamics

On the efficiency of the golf swing

Rod White

American Journal of Physics -- December 2006 -- Volume 74, Issue 12, pp. 1088 | Cited 6 times

Online Publication Date: Nov 2006

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A non-driven double pendulum model is used to explain the principle underlying the surprising efficiency of the golf swing. The principle can be described as a parametric energy transfer between the arms and the club head due to the changing moment of inertia of the club. The transfer is a consequence of conservation of energy and angular momentum. Because the pendulum is not driven by an external force, it shows that the golfer need do little more than accelerate the arms with the wrists cocked and let the double pendulum transfer kinetic energy to the club head. A driven double pendulum model is used to study factors affecting the efficiency of a real golf swing. It is concluded that the wrist-cock angle is the most significant efficiency-determining parameter under the golfer’s control and that improvements in golf technology have had a significant impact on driving distance.
Show PACS
01.55.+b General physics
47.00.00 Fluid dynamics

The Rayleigh-Taylor instability

A. R. Piriz, O. D. Cortázar, J. J. López Cela, and N. A. Tahir

American Journal of Physics -- December 2006 -- Volume 74, Issue 12, pp. 1095 | Cited 21 times

Online Publication Date: Nov 2006

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A new approach to the Rayleigh-Taylor instability is presented that yields exact solutions for the simplest cases and provides approximate but still very accurate analytical expressions for important and more complex cases involving nonideal fluids. The approach is based on Newton’s second law and allows for an intuitive and physically appealing explanation of the mechanisms underlying the instability.
Show PACS
47.00.00 Fluid dynamics

Robotics projects as an integration exercise in a sophomore-junior level analog electronics course

Richard E. Stevens and John M. Larkin

American Journal of Physics -- December 2006 -- Volume 74, Issue 12, pp. 1099 | Cited 1 time

Online Publication Date: Nov 2006

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A robotics project involving the custom design and implementation of analog transducers into LEGO robots has been added to our sophomore-junior level analog electronics course. This project allows the integration of circuit components whose properties and applications are learned throughout the course into a final unified project, motivates students to exercise initiative and creativity, and demonstrates a current application of analog electronics. Feedback both from students and the campus community has been very positive.
Show PACS
07.00.00 Instruments, apparatus, and components common to several branches of physics and astronomy

How large is the “natural” magnetic moment?

Barry R. Holstein

American Journal of Physics -- December 2006 -- Volume 74, Issue 12, pp. 1104 | Cited 3 times

Online Publication Date: Nov 2006

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The “natural” magnetic moment of a particle of spin S is generally assumed to be that given by the Belinfante conjecture and has the gyromagnetic ratio g=1∕S. Thus, for the spin 1∕2 electron we find the Dirac value ge=2. However, in the standard model the charged W-boson, a spin-one particle, is found to have gW+=2. We discuss this result and argue that the natural value for any particle of spin S should be g=2, independent of spin.
Show PACS
03.65.-w Quantum mechanics

An analytic solution from a spherical gamma emitter

William J. Atkinson and Ivan A. Brezovich

American Journal of Physics -- December 2006 -- Volume 74, Issue 12, pp. 1112

Online Publication Date: Nov 2006

Full Text: Read Online (HTML) | Download PDF

Show Abstract
An analytic solution for the fluence rate of primary (non-scattered) gamma rays emerging from a spherical radioactive source is presented. The solution takes self-attenuation into account and is valid at any distance from the source. It is derived using elementary integral calculus and does not require special functions. The key to the relatively simple solution is a shift of the center of the sphere along the z-axis by a distance equal to the radius, so that the surface of the sphere passes through the origin of the coordinate system.
Show PACS
20.00.00 NUCLEAR PHYSICS

Gravitational orbits in one dimension

Martin McCall

American Journal of Physics -- December 2006 -- Volume 74, Issue 12, pp. 1115 | Cited 1 time

Online Publication Date: Nov 2006

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The analytic solution of a body falling an arbitrary distance toward a gravitational source is presented. This problem has apparently received little attention in textbooks. The solution can be extended smoothly through the singularity at the origin to form a class of trajectories that we call singular orbits. Trajectories in phase space have singular branches, yet cycle in a finite time. We calculate the period of oscillation about the singularity confirming that the singular orbits obey Kepler’s third law. Viewed as geodesics in a Newtonian 1+1 spacetime, the geodesic deviation equation is derived and solved analytically, providing an excellent example of curvature physics in Newtonian spacetime. The results are used to estimate the duration during which a freely falling local frame can be considered inertial. A numerical investigation with damping included shows that a final state is reached in which the particle is confined to the origin, but acquires infinite speed during each pass. We show via some examples, the pedagogical applications of the solution.
Show PACS
47.00.00 Fluid dynamics

Finite line of charge

Robert J. Rowley

American Journal of Physics -- December 2006 -- Volume 74, Issue 12, pp. 1120 | Cited 3 times

Online Publication Date: Nov 2006

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A finite line of uniform charge is either ignored or handled incompletely in most textbooks. New simple and practical expressions are presented for the electric potential and electric field for this charge distribution. The equipotentials are shown to be prolate ellipsoids and the electric field lines follow hyperboloids confocal to the ellipsoids. The common foci are shown to be the endpoints of the charged line segment. These geometries are demonstrated with simple VPython programs.
Show PACS
41.00.00 Electromagnetism; electron and ion optics

The entropy of mixing and assimilation: An information-theoretical perspective

Arieh Ben-Naim

American Journal of Physics -- December 2006 -- Volume 74, Issue 12, pp. 1126

Online Publication Date: Nov 2006

Full Text: Read Online (HTML) | Download PDF

Show Abstract
It is claimed that the quantity −k∑xi ln xi, the so-called “entropy of mixing,” has nothing to do with the mixing process, and that, contrary to the accepted view, mixing is not an irreversible process. Instead, the process of deassimilation is introduced, and it is shown that it is an inherently irreversible process. The information-theoretical perspective of these statements is discussed for classical and quantum-mechanical systems of noninteracting particles.
Show PACS
05.00.00 Statistical physics, thermodynamics, and nonlinear dynamical systems

Understanding stable levitation of superconductors from intermediate electromagnetics

A. Badía-Majós

American Journal of Physics -- December 2006 -- Volume 74, Issue 12, pp. 1136 | Cited 8 times

Online Publication Date: Nov 2006

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Levitation experiments with superconductors in the Meissner state are hindered by low stability except for specifically designed configurations. In contrast, magnetic force experiments with strongly pinned superconductors and permanent magnets display high stability, allowing the demonstration of striking effects, such as lateral or inverted levitation. These facts are explained by using a variational theory. Illustrations based on calculated magnetic field lines for various configurations are presented. They provide a qualitative physical understanding of the stability features.
Show PACS
41.00.00 Electromagnetism; electron and ion optics
74.00.00 Superconductivity
back to top
RSS Feeds

Assessment of difficulties of some conceptual areas from electricity and magnetism using the Conceptual Survey of Electricity and Magnetism

Maja Planinic

American Journal of Physics -- December 2006 -- Volume 74, Issue 12, pp. 1143 | Cited 3 times

Online Publication Date: Nov 2006

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The Conceptual Survey of Electricity and Magnetism (CSEM) covers a large conceptual domain and gives many opportunities for comparing the difficulties of different conceptual areas in electricity and magnetism. Six conceptual areas were identified in the CSEM that are represented by groups of four to six questions each. The CSEM was administered as a posttest to 84 Croatian students in a calculus-based general physics course at the University of Zagreb. The average difficulties in the six conceptual areas were compared to the average difficulties of the same conceptual areas of American students enrolled in algebra-based or calculus-based general physics courses. The difficulties of the conceptual areas show similar trends for the three groups of students. The most difficult area was found to be electromagnetic induction, followed by Newton’s laws in the context of electricity and magnetism, together with the electric potential and energy. The comparison of pretest and posttest results suggests that instruction in both algebra-based and calculus-based courses is not efficient in reducing the pretest difficulties of the conceptual areas; however, the impact of instruction differs among conceptual areas.
Show PACS
01.40.Fk Research in physics education
back to top
RSS Feeds

Erratum: “Golfer's dilemma” [Am. J. Phys. 74 (6), 497–501 (2006)]

Marco Gualtieri, Tadashi Tokieda, L. Advis-Gaete, B. Carry, E. Reffet, and Claude Guthmann

American Journal of Physics -- December 2006 -- Volume 74, Issue 12, pp. 1149

Online Publication Date: Nov 2006

Full Text: Read Online (HTML) | Download PDF

Abstract Unavailable
Show PACS
99.10.-x Errata and other corrections
47.00.00 Fluid dynamics
01.55.+b General physics
back to top
RSS Feeds

BOOKS RECEIVED

American Journal of Physics -- December 2006 -- Volume 74, Issue 12, pp. 1150

Online Publication Date: Nov 2006

Full Text: Read Online (HTML) | Download PDF

Abstract Unavailable
back to top
RSS Feeds

Volume 74 Index

American Journal of Physics -- December 2006 -- Volume 74, Issue 12, pp. I1

Full Text: Read Online (HTML) | Download PDF

multimedia

Abstract Unavailable
Close

Your Recent History Recent History Help

Recently Viewed

  1. Differential aging from acceleration: An explicit formula
  2. Padé–Laplace analysis of signal averaged voltage decays obtained from a simple circuit
  3. The “Cheerios effect”
  4. Relation between students’ problem-solving performance and representational format
  5. A direct comparison of conceptual learning and problem solving ability in traditional and studio sty...

AAPT on:

close