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Sep 2005

Volume 73, Issue 9, pp. 805-896

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Resource Letter MP-1: The Manhattan Project and related nuclear research

B. Cameron Reed

American Journal of Physics -- September 2005 -- Volume 73, Issue 9, pp. 805 | Cited 1 time

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This Resource Letter provides a guide to literature on the Manhattan Project and related nuclear research. Books and journal articles are cited for the following topics: general works, technical works, biographical and autobiographical works, the German nuclear program, and technical papers of historical interest. A list of videos and websites dealing with the Manhattan Project, nuclear weapons, and nuclear issues is also given.
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01.40.Fk Research in physics education
01.30.Rr Surveys and tutorial papers; resource letters

Increase in friction force with sliding speed

Rod Cross

American Journal of Physics -- September 2005 -- Volume 73, Issue 9, pp. 812

Online Publication Date: Aug 2005

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A block sliding down an inclined plane normally accelerates. However, if the friction force increases with speed, then the block can slide at a constant terminal speed in a manner similar to the fall of an object through a fluid. Measurements of the increase in the coefficient of friction for tennis ball cloth sliding on a smooth surface are described over speeds varying by a factor of 9000. For the low speed measurements, the ball cloth was attached to the bottom of a weighted box and pulled along a horizontal surface by a constant horizontal force. Results at higher speeds were obtained by bouncing a tennis ball off the surface. © 2005 American Association of Physics Teachers.
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01.50.My Demonstration experiments and apparatus

The “Cheerios effect”

Dominic Vella and L. Mahadevan

American Journal of Physics -- September 2005 -- Volume 73, Issue 9, pp. 817 | Cited 33 times

Online Publication Date: Aug 2005

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Objects that float at the interface between a liquid and a gas interact because of interfacial deformation and the effect of gravity. We highlight the crucial role of buoyancy in this interaction, which, for small particles, prevails over the capillary suction that often is assumed to be the dominant effect. We emphasize this point using a simple classroom demonstration, and then derive the physical conditions leading to mutual attraction or repulsion. We also quantify the force of interaction in particular instances and present a simple dynamical model of this interaction. The results obtained from this model are validated by comparison to experimental results for the mutual attraction of two identical spherical particles. We consider some of the applications of the effect that can be found in nature and the laboratory. © 2005 American Association of Physics Teachers.
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01.50.My Demonstration experiments and apparatus
01.50.Pa Laboratory experiments and apparatus

Demonstration experiments on nondiffracting beams generated by thermal light

Lorenzo Basano and Pasquale Ottonello

American Journal of Physics -- September 2005 -- Volume 73, Issue 9, pp. 826 | Cited 4 times

Online Publication Date: Aug 2005

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Nondiffracting (Bessel) beams are normally generated using fully coherent light (a laser). Yet their distinctive properties (nondiffraction and self-reconstruction) can be obtained using a common halogen lamp as the primary source. Other experiments, for example, the creation of periodic intensity modulations along the optical axis, require a source with a much narrower spectrum. We present demonstrations that show that thermal light is useful for explaining several properties of a Bessel-beam generator and may help students to understand some issues of modern coherence theory. © 2005 American Association of Physics Teachers.
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01.50.My Demonstration experiments and apparatus
42.25.Kb Coherence

Hamilton’s principle: Why is the integrated difference of the kinetic and potential energy minimized?

Alberto G. Rojo

American Journal of Physics -- September 2005 -- Volume 73, Issue 9, pp. 831

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Why is the integrated difference of the kinetic and potential energies the quantity to be minimized in Hamilton’s principle? I use simple arguments to convert the problem of finding the path of a particle connecting two points to that of finding the minimum potential energy of a string. The mapping implies that the configuration of a nonstretchable string of variable tension corresponds to the spatial path dictated by the principle of least action; that of a stretchable string in space–time is the one dictated by Hamilton’s principle. This correspondence provides the answer to the question.
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01.40.-d Education
45.20.Jj Lagrangian and Hamiltonian mechanics

Spectroscopy versus interferometry: Resolving small changes

Brian J. Zadler, Alexandre Grêt, and John A. Scales

American Journal of Physics -- September 2005 -- Volume 73, Issue 9, pp. 837 | Cited 4 times

Online Publication Date: Aug 2005

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Some experiments are conveniently performed in the time domain, some in the frequency domain, and some use a hybrid approach. Does the domain make any difference in the ultimate resolution of the experiment? Or can the details of the experiment always be tweaked so that the different approaches give the same answer? We consider a simple optics experiment and consider both time and frequency measurements and take into account the influence of noise, finite dynamic range, attenuation, and the duration of the measurement. © 2005 American Association of Physics Teachers.
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01.50.Pa Laboratory experiments and apparatus
07.60.Ly Interferometers

Inexpensive two-dimensional measuring device for cryogenic temperatures

A. Grau Carles

American Journal of Physics -- September 2005 -- Volume 73, Issue 9, pp. 845

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A simple device for measuring thermal deformations in two-dimensional samples cooled to liquid nitrogen temperatures is described. The measurement consists of adding liquid nitrogen to a transparent quartz tray, and then scanning the sample from the bottom with a flatbed scanner. As a test of the device, the thermal contraction of aluminum from room temperature to 77 K is measured. The application of Grüneisen’s approximation leads to good agreement between the calculated and tabulated contraction percentages.
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01.50.-i Educational aids
07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment

Design of a low cost Zimm–Crothers viscometer: From theory to experiment

L. Courbin, G. Cristobal, M. Winckert, and P. Panizza

American Journal of Physics -- September 2005 -- Volume 73, Issue 9, pp. 851 | Cited 5 times

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To accurately measure low viscosities of liquids, we describe how a Zimm–Crothers viscometer works and how to build it. The viscometer involves the action of a rotating magnetic field on a metallic cylinder floating on the liquid to be studied. The principles of electromagnetism and fluid mechanics involved make the viscometer an excellent tool for undergraduate laboratory courses and for measuring the shear viscosity of low viscous fluids. We discuss the advantages and limitations of this inexpensive and easy to use apparatus compared to other classical techniques. Calibrations with Newtonian fluids are explained and experiments with Non-Newtonian materials are discussed.
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01.50.Qb Laboratory course design, organization, and evaluation
66.20.-d Viscosity of liquids; diffusive momentum transport
47.50.-d Non-Newtonian fluid flows
62.10.+s Mechanical properties of liquids

A simple Fermi-Dirac integrating circuit

Dennis Hite, Timothy B. Boykin, Nagendra Singh, and Dashen Shen

American Journal of Physics -- September 2005 -- Volume 73, Issue 9, pp. 856

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We present a simple circuit that performs Fermi-Dirac integration. The core of the circuit is a differential amplifier that we show is a model of a Fermi-Dirac system. The construction and characterization of the circuit requires students to apply knowledge of device physics, transistor circuit theory, and signal processing. The circuit construction is relatively simple and requires only a few components found in most electronics laboratories.
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01.50.Pa Laboratory experiments and apparatus
05.30.Fk Fermion systems and electron gas
85.30.Pq Bipolar transistors

Calculation of x-ray wave fields in perfect crystals by applying Riemann’s method to solve the Takagi-Taupin equations

C. Palmisano and G. Zosi

American Journal of Physics -- September 2005 -- Volume 73, Issue 9, pp. 860 | Cited 1 time

Online Publication Date: Aug 2005

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The Takagi-Taupin equations are a set of partial differential equations that are fundamental in the dynamical theory of x-ray diffraction. We show how they can be manipulated to make them suitable for the application of Riemann’s method and present in detail the steps leading to their solution. To help readers gain insight into coherent x-ray wave fields, we calculate the intensity distribution of x-ray beams from mono- and polylithic perfect silicon single crystals. As an example of the interplay between wave fields, we illustrate the Pendellösung effect. We did some of the algebraic manipulations and most of the numerical calculations by using Mathematica. © 2005 American Association of Physics Teachers.
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01.40.-d Education
61.66.Bi Elemental solids
02.30.Jr Partial differential equations

Padé–Laplace analysis of signal averaged voltage decays obtained from a simple circuit

Edward H. Hellen

American Journal of Physics -- September 2005 -- Volume 73, Issue 9, pp. 871

Online Publication Date: Aug 2005

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The Padé–Laplace method is an interesting yet relatively unknown method for determining the exponential time constants in a decaying signal. We apply it to data from a simple electronic circuit specifically designed for investigations of signal averaging. Possible decays of the voltage include single, multi-exponential, and predominantly logarithmic. Students in our computer-interfacing course write a LABVIEW program that collects the data and performs the signal averaging. © 2005 American Association of Physics Teachers.
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01.50.ht Instructional computer use
84.30.Bv Circuit theory
02.60.Ed Interpolation; curve fitting

Differential aging from acceleration: An explicit formula

E. Minguzzi

American Journal of Physics -- September 2005 -- Volume 73, Issue 9, pp. 876 | Cited 7 times

Online Publication Date: Aug 2005

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We consider a clock paradox where an observer leaves an inertial frame, is accelerated, and after an arbitrary trip returns. We discuss a simple equation that gives an explicit relation in 1+1 dimensions between the time elapsed in the inertial frame and the acceleration measured by the accelerating observer during the trip. A non-closed trip with respect to an inertial frame appears closed with respect to another suitable inertial frame. We use this observation to define the differential aging as a function of proper time. The reconstruction problem of special relativity is discussed and it is shown that its solution would allow the construction of an inertial clock. © 2005 American Association of Physics Teachers.
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01.50.-i Educational aids
03.30.+p Special relativity
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Comment on “Paradoxical behavior of an infinite ladder network of inductors and capacitors,” by S. J. van Enk [Am. J. Phys. 68, 854–856 (2000)]

Ali Ümit Keskin, Deniz Pazarci, and Cevdet Acar

American Journal of Physics -- September 2005 -- Volume 73, Issue 9, pp. 881 | Cited 2 times

Online Publication Date: Aug 2005

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Abstract Unavailable
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01.50.-i Educational aids
84.30.Vn Filters
84.32.Hh Inductors and coils; wiring
84.32.Tt Capacitors
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Measurements of K x-ray fluorescence parameters

A. S. Bennal, P. D. Shidling, N. M. Badiger, S. R. Thontadarya, and B. Hanumaiah

American Journal of Physics -- September 2005 -- Volume 73, Issue 9, pp. 883 | Cited 6 times

Online Publication Date: Aug 2005

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A simple x-ray fluorescence experiment suitable for graduate and undergraduate laboratories is described. The experiment uses a NaI(Tl) x-ray spectrometer, a weak 57Co radioactive source (∼105 Bq), and medium-Z targets of silver, cadmium, indium, and tin. The K x-ray fluorescence yield, ωk, and K x-ray production cross section, σk, are measured for these targets. Accurate results are achieved by adopting a 2π detection geometry and by optimizing target dimensions for this experimental configuration. The experiment can be completed in 4 h and is suitable for student laboratories. © 2005 American Association of Physics Teachers.
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01.50.Pa Laboratory experiments and apparatus

A computer-based physics laboratory apparatus: Signal generator software

Tharest Thanakittiviroon and Sompong Liangrocapart

American Journal of Physics -- September 2005 -- Volume 73, Issue 9, pp. 887

Online Publication Date: Aug 2005

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This paper describes a computer-based physics laboratory apparatus to replace expensive instruments such as high-precision signal generators. This apparatus uses a sound card in a common personal computer to give sinusoidal signals with an accurate frequency that can be programmed to give different frequency signals repeatedly. An experiment on standing waves on an oscillating string uses this apparatus. In conjunction with interactive lab manuals, which have been developed using personal computers in our university, we achieve a complete set of low-cost, accurate, and easy-to-use equipment for teaching a physics laboratory. © 2005 American Association of Physics Teachers.
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01.50.Lc Laboratory computer use
01.50.Pa Laboratory experiments and apparatus
01.40.-d Education
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Edward Teller: The Real Dr. Strangelove

Peter Goodchild, Author and Charles R. Loeber, Reviewer

American Journal of Physics -- September 2005 -- Volume 73, Issue 9, pp. 893

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Abstract Unavailable
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01.30.Vv Book reviews
01.40.-d Education
01.60.+q Biographies, tributes, personal notes, and obituaries

The Prism and the Pendulum: The Ten Most Beautiful Experiments in Science.

Robert P. Crease, Author and Philippe M. Binder, Reviewer

American Journal of Physics -- September 2005 -- Volume 73, Issue 9, pp. 895

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Abstract Unavailable
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01.30.Vv Book reviews
01.50.Pa Laboratory experiments and apparatus
01.40.Di Course design and evaluation
07.10.-h Mechanical instruments and equipment
42.79.Bh Lenses, prisms and mirrors

Books Received

American Journal of Physics -- September 2005 -- Volume 73, Issue 9, pp. 896

Online Publication Date: Aug 2005

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Abstract Unavailable
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01.30.Vv Book reviews
01.40.-d Education
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