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Nov 2009

Volume 47, Issue 8, pp. 484-560

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What Should We Expect Students to Learn?

Noah Finkelstein, Eric Mazur, and Nathaniel Lasry

The Physics Teacher -- November 2009 -- Volume 47, Issue 8, pp. 484 | Cited 1 time

Online Publication Date: Oct 2009

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A rejoinder to Sobel's comment on “Are most people too dumb for physics?” We read Michael Sobel's response with much interest and appreciate his enthusiasm and commitment to physics education. Yet, we continue to find that our goals and methods differ markedly. Foremost, because we do not agree that physics is a “different category” of hard which is accessible to a select few (i.e., “a certain sort of very bright student”), we cannot agree that ordinary, nonscience students must be taught a different kind of physics. We object to the idea of two “types” of physics—one for the layperson and one for the specialist. Physics must have relevance for everyone.
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01.40.Fk Research in physics education
01.75.+m Science and society

Teaching Special Relativity

James J. Carr

The Physics Teacher -- November 2009 -- Volume 47, Issue 8, pp. 485

Online Publication Date: Oct 2009

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I was not one of those many AAPT members to whom Lawrence Ruby refers, that in 2007 received Elisha Huggins' booklet containing the first chapter of a physics textbook espousing the new educational philosophy of teaching special relativity first in elementary physics.
Show PACS
01.40.gb Teaching methods and strategies
01.30.mp Textbooks for undergraduates

Editor's Note: Correction to the International Year of Astronomy trading cards (series 1) included with the September issue.

The Physics Teacher -- November 2009 -- Volume 47, Issue 8, pp. 485

Online Publication Date: Oct 2009

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Abstract Unavailable
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01.10.Hx Physics organizational activities
01.30.-y Physics literature and publications
99.10.Cd Errata
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Remembering Len Jossem

Tony French

The Physics Teacher -- November 2009 -- Volume 47, Issue 8, pp. 486

Online Publication Date: Oct 2009

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Abstract Unavailable
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01.60.+q Biographies, tributes, personal notes, and obituaries
01.65.+g History of science
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DEEP WELL

Paul Hewitt

The Physics Teacher -- November 2009 -- Volume 47, Issue 8, pp. 488 | Cited 1 time

Online Publication Date: Oct 2009

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Abstract Unavailable
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01.50.Kw Techniques of testing
01.50.Rt Physics tournaments and contests
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Establishing Real‐World Connections for a Better Understanding of Circuits

David Bonner

The Physics Teacher -- November 2009 -- Volume 47, Issue 8, pp. 490

Online Publication Date: Oct 2009

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Many physics teachers would agree that students making real‐world connections is a critical aspect of learning physics, but what does this really mean? Merely seeing a real‐world application of a physical concept does not necessarily allow students to incorporate the concept into the way they perceive their world. It is not just seeing the application that makes the real‐world connection, but establishing personal relevance to that student's life that is a key to learning physics. This paper describes a constructivist activity in which students design and assemble a common and personally relevant electrical device—the power strip.
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01.40.gb Teaching methods and strategies
01.50.Pa Laboratory experiments and apparatus

Student Projects in Cosmic Ray Detection

W. Brouwer, J. Pinfold, R. Soluk, B. McDonough, V. Pasek, and Zheng Bao‐shan

The Physics Teacher -- November 2009 -- Volume 47, Issue 8, pp. 494

Online Publication Date: Oct 2009

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The Alberta Large‐area Time‐coincidence Array (ALTA) study has been in existence for about 10 years under the direction of Jim Pinfold of the Centre for Particle Physics at the University of Alberta.1 The purpose of the ALTA project is to involve Alberta high schools, and primarily their physics classes, to assist in the detection of the presence of cosmic ray bursts in different Alberta locations. These cosmic rays involve highspeed elementary particles, many from far outside our solar system and even from outside our galaxy. These particles collide with the particles in our atmosphere, break up these molecules into rather exotic elementary particles which often reach the surface of the Earth and can be detected by fairly simple equipment. One of the objectives of ALTA is to determine the nature of some of the most energetic cosmic ray particles whose origin is still not known. Recently 2the Pierre Auger Collaboration has confirmed that the highest energy cosmic rays appear to be coming from nearby galaxies. The mechanism for their production is still not well understood.
Show PACS
01.40.gb Teaching methods and strategies
01.50.-i Educational aids
01.75.+m Science and society

It Is Worth Thoroughly Looking at the Computer Display

Yaakov Kraftmakher

The Physics Teacher -- November 2009 -- Volume 47, Issue 8, pp. 499

Online Publication Date: Oct 2009

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Two useful observations are possible when thoroughly looking at the cathode‐ray display of a computer. First, the structure of a color image is seen with a moderate magnification. Second, the decay of different phosphors corresponding to the red, green, and blue primary colors is observable with a photodiode and oscilloscope.
Show PACS
01.40.gb Teaching methods and strategies
01.50.ht Instructional computer use
01.50.My Demonstration experiments and apparatus

Radial Motion of Two Mutually Attracting Particles

Carl E. Mungan

The Physics Teacher -- November 2009 -- Volume 47, Issue 8, pp. 502

Online Publication Date: Oct 2009

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A pair of masses or opposite‐sign charges released from rest will move directly toward each other under the action of the inverse‐distance‐squared force of attraction between them. An exact expression for the separation distance as a function of time can only be found by numerically inverting the solution of a differential equation. A simpler, approximate formula can be obtained by combining dimensional analysis, Kepler's third law, and the familiar quadratic dependence of distance on time for a mass falling near Earth's surface. These exact and approximate results are applied to several interesting examples: the flight time and maximum altitude attained by an object fired straight upward from Earth's surface; the time required for an asteroid of known starting position and speed to cross Earth's orbit if it is bearing toward the Sun; and the collision time of two oppositely charged particles starting from rest.

“Back of the Spoon” Outlook of Coanda Effect

T. López‐Arias, L. M. Gratton, S. Bon, and S. Oss

The Physics Teacher -- November 2009 -- Volume 47, Issue 8, pp. 508

Online Publication Date: Oct 2009

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The tendency of fluids to follow, in certain conditions, curved profiles is often referred to as the Coanda effect. A simple experiment modeling the common teapot effect, the curling of the liquid around the beak when it is poured, can be used in the classroom to illustrate simple dynamic principles and basic fluid dynamics concepts as well.1
Show PACS
01.40.gb Teaching methods and strategies
01.50.Pa Laboratory experiments and apparatus
47.15.Rq Laminar flows in cavities, channels, ducts, and conduits
FREE

A Simple Demonstration of Back emf

Lou Turner

The Physics Teacher -- November 2009 -- Volume 47, Issue 8, pp. 513

Online Publication Date: Oct 2009

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In discussing motors, one college textbook says, “As the coil (of a motor) rotates in a magnetic field, a back emf is generated that tends to counter the emf that supplies the current.” This is a true statement, but it does little to enhance student understanding of how and why it is created. In this paper, I will explain how to take students step by step through the creation of what the experts call “back emf” and then describe a simple experiment that clearly demonstrates its existence.
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01.40.gb Teaching methods and strategies
01.50.My Demonstration experiments and apparatus
41.20.-q Applied classical electromagnetism

Hanging an Airplane: A Case Study in Static Equilibrium

Debora M. Katz

The Physics Teacher -- November 2009 -- Volume 47, Issue 8, pp. 516

Online Publication Date: Oct 2009

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Our classrooms are filled with engineering majors who take a semester‐long course in static equilibrium. Many students find this class too challenging and drop their engineering major. In our introductory physics class, we often breeze through static equilibrium; to physicists equilibrium is just a special case of Newton's second law. While it is difficult to find more time in the syllabus for any one topic, a hands‐on case study may help students to develop their physical intuition about static equilibrium and may help them to succeed in their subsequent classes. This article describes a hands‐on case study that you may wish to use in your classroom. (You may also wish to check a case study involving a boat published in this journal in the 1990s.1) The hands‐on case study presented here can be easily modified to work at the high school or introductory college level. There are three major components: I) planning, II) doing, and III) calculating.
Show PACS
01.40.gb Teaching methods and strategies
01.50.My Demonstration experiments and apparatus
01.55.+b General physics

Teaching General Relativity to the Layperson

Mark Egdall

The Physics Teacher -- November 2009 -- Volume 47, Issue 8, pp. 522

Online Publication Date: Oct 2009

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This paper describes a lay course on general relativity (GR) given at the Osher Lifelong Learning Institute at Florida International University. It is presented in six hour‐and‐a‐half weekly sessions. Other courses offered by the author include special relativity (which precedes the course described here), quantum theory, and cosmology. Students are people 50 and older, mostly retired or semi‐retired like me. They come from all walks of life, including medical doctors, ballet directors, educators, cruise line executives, and poets. Most are college educated, but with little or no formal physics education. A few have technical backgrounds, e.g., chemistry or physics.
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01.40.gb Teaching methods and strategies
01.30.Vv Book reviews

Capillary Rise in a Wedge

M. Piva

The Physics Teacher -- November 2009 -- Volume 47, Issue 8, pp. 528

Online Publication Date: Oct 2009

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In introductory‐level physics courses, the concept of surface tension is often illustrated using the example of capillary rise in thin tubes.1 In this paper I describe experiments conducted using a planar geometry created with two small plates forming a thin wedge (see Fig. 1). The distribution of the fluid entering the wedge can be studied as a function of the wedge angle.
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01.50.My Demonstration experiments and apparatus
47.55.nb Capillary and thermocapillary flows
FREE

Steel Spheres and Skydiver — Terminal Velocity

J. Costa Leme, C. Moura, and Cíntia Costa

The Physics Teacher -- November 2009 -- Volume 47, Issue 8, pp. 531

Online Publication Date: Oct 2009

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This paper describes the use of open source video analysis software in the study of the relationship between the velocity of falling objects and time. We discuss an experiment in which a steel sphere falls in a container filled with two immiscible liquids. The motion is similar to that of a skydiver falling through air.
Show PACS
01.40.gb Teaching methods and strategies
01.50.Pa Laboratory experiments and apparatus
01.50.ht Instructional computer use

Measuring the Radius of the Earth from a Mountain Top Overlooking the Ocean

Dhevan Gangadharan

The Physics Teacher -- November 2009 -- Volume 47, Issue 8, pp. 533 | Cited 2 times

Online Publication Date: Oct 2009

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A clear view of the ocean may be used to measure the radius of the Earth. To an observer looking out at the ocean, the horizon will always form some angle θ with the local horizontal plane. As the observer's elevation h increases, so does the angle θ (see Fig. 1). From measurements of the elevation h and the angle θ, the radius R of the Earth may be found. This paper describes an experiment in which measurements were taken at an elevation of approximately 485 m in the Santa Monica hills of Los Angeles, CA. The average refraction-corrected value for the radius of the (assumed spherical) Earth was found to be 6100 ± 420 km. The accepted value at the equator is 6380 km.
Show PACS
01.40.gb Teaching methods and strategies
01.55.+b General physics

Inexpensive Strobe-like Photographs

Emil L. Medeiros, Odilon A. P. Tavares, and Sérgio B. Duarte

The Physics Teacher -- November 2009 -- Volume 47, Issue 8, pp. 536

Online Publication Date: Oct 2009

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This paper reports on a technique the authors have developed to produce and analyze, at very low cost, good quality strobe-like photographs like the one shown in Figs. 1(a) and 1(b). While the concept is similar to the one described by Graney and DiNoto,1 the strategy described here benefits from recent advances in the fields of digital photography and related software to significantly reduce the costs, simplify the production process, and enhance the final quality of photographs of this type, as well as to obtain greater accuracy in measurements made with them.
Show PACS
01.40.gb Teaching methods and strategies
01.50.Pa Laboratory experiments and apparatus
FREE

Using Ethnic Art to Emphasize Laws of Reflection

Madhuri Bapat

The Physics Teacher -- November 2009 -- Volume 47, Issue 8, pp. 542

Online Publication Date: Oct 2009

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The Kolam (Rangolee) art (Fig. 1) from Southern India and Sona drawings (Fig. 2) from Africa show the similarity of lines going around the dots. Kolam is usually drawn, with paste made up of rice powder, on the floor in front of a house. Typically girls draw these in India on occasions such as welcoming the spring season, weddings, or birthdays. Sona drawings are drawn in the sand using fingers. Typically young boys in Africa were taught to draw these as they went through puberty. They used to impress their masters by drawing these designs quickly in sand and erasing them afterwards. So Europeans never learned these designs. Due to slavery this art or knowledge has disappeared.
Show PACS
01.40.gb Teaching methods and strategies
01.55.+b General physics
01.50.-i Educational aids
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Cyclone on a Turntable: Illustrations of the Coriolis Force

Ole Anton Haugland

The Physics Teacher -- November 2009 -- Volume 47, Issue 8, pp. 546

Online Publication Date: Oct 2009

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The description of motion in a noninertial reference frame, and especially the Coriolis force, is a topic that often comes up even when it is not in the curriculum. Sometimes students may have seen a Foucault pendulum at a museum or they may have heard a discussion about the draining of bathtubs. At those times it would be nice to be able to give a simple and clear demonstration in the next lesson. At a more advanced level, the description of the Coriolis and the centrifugal force is a nice illustration of the use of vector algebra.
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01.50.My Demonstration experiments and apparatus
45.20.D- Newtonian mechanics
45.40.Bb Rotational kinematics
92.00.00 Hydrospheric and atmospheric geophysics
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Parallel in Geometry Does Not Necessarily Mean Parallel in Physics

Andrzej Sokolowski

The Physics Teacher -- November 2009 -- Volume 47, Issue 8, pp. 550

Online Publication Date: Oct 2009

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While distinguishing between parallel and series connections, some students refer to geometrical interpretation of parallel lines to identify parallel connection of resistors.
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01.40.ek Secondary school
01.55.+b General physics
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A Slide Show

Boris Korsunsky, Column Editor

The Physics Teacher -- November 2009 -- Volume 47, Issue 8, pp. 551

Online Publication Date: Oct 2009

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A block is placed on a long and wide inclined plane that makes angle θ with the horizontal. The coefficient of kinetic friction between the block and the plane is μktanθ. After a quick push, the block acquires velocity v0 that makes angle α with the line of fastest descent. Find the time interval τ during which the block is in motion.
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01.50.Kw Techniques of testing
01.50.Rt Physics tournaments and contests
01.40.J- Teacher training
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FREE

Fermi Questions

Larry Weinstein, Column Editor

The Physics Teacher -- November 2009 -- Volume 47, Issue 8, pp. 551

Online Publication Date: Oct 2009

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How much energy would the United States generate per year if we connected all of our stair-steppers, rowing machines, treadmills, etc. to electrical generators? How much money would one person save by generating his or her own electricity that way? Assume that the number of people working out does not change when we do this.
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01.50.Kw Techniques of testing
01.50.Rt Physics tournaments and contests
01.40.J- Teacher training
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Outta This World

Diane Riendeau

The Physics Teacher -- November 2009 -- Volume 47, Issue 8, pp. 552

Online Publication Date: Oct 2009

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Some physics misconceptions arise due to the fact that in our everyday world, air resistance and friction are always present. By taking an experiment into a “zero gravity” or “micro gravity” situation, we can often greatly reduce the effect of these undesired forces and dispel misconceptions.
I offer up these links from various space missions because they are “outta this world.”
Special thanks to Jennifer Groppe from Maret School in Washington, D.C., for submitting all these video links. If you have video links you'd like to share, please email them with a brief description to Diane Riendeau at driendeau@dist113.org.
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01.40.gb Teaching methods and strategies
01.50.ht Instructional computer use
01.55.+b General physics
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Collective Wisdom Made Visible

Patricia Blanton, Column Editor

The Physics Teacher -- November 2009 -- Volume 47, Issue 8, pp. 553

Online Publication Date: Oct 2009

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At the end of a teaching unit and prior to an assessment of what students have learned, many teachers will take time to review the materials with the class. During the typical review session, the major concepts are summarized, sample problems are worked, and students are given a chance to take notes and ask questions about things they don't understand. I recently observed a teacher using a very different review technique and was very impressed with the student involvement during the session.
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01.40.J- Teacher training
01.40.gb Teaching methods and strategies
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A Spherical Boomerang

Yasuo Ogawara

The Physics Teacher -- November 2009 -- Volume 47, Issue 8, pp. 555

Online Publication Date: Oct 2009

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Abstract Unavailable
Show PACS
01.50.My Demonstration experiments and apparatus
01.40.gb Teaching methods and strategies
01.55.+b General physics
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Sustainable Energy — Without the hot air

Dan MacIsaac, Column Editor

The Physics Teacher -- November 2009 -- Volume 47, Issue 8, pp. 556

Online Publication Date: Oct 2009

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Reader John Roeder writes about a website associated with David MacKay's book Sustainable Energy—Without the hot air. The book is a freely downloadable PDF (or purchasable) book describing an analysis detailing a low-carbon renewable energy transformation route for a large, modern first world industrial country (the United Kingdom). Written for the layman, the work uses vernacular language, e.g., energy consumption and production in a series of bar charts detailing the impacts of necessary strategies such as population reduction, lifestyle changes, and technology changes. MacKay notes that most reasonable plans have large nuclear and “clean coal” or other carbon capture components, lots of pumped heat, wind, and much efficiency improvement. He debunks some sacred cows (roof-mounted micro-turbines; hydrogen-powered cars) while pointing out simple effective technologies such as roof-mounted solar water heaters. Similar modest changes in the U.S. (painting roofs white in the southern half of the country) have strong impacts. MacKay claims that he “doesn't advocate any particular plan or technology,” but “tells you how many bricks are in the lego box, and how big each brick is” so readers can start making planning decisions.
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01.50.H- Computers in education
01.30.Xx Publications in electronic media

Technology Review, published by MIT

Dan MacIsaac, Column Editor

The Physics Teacher -- November 2009 -- Volume 47, Issue 8, pp. 556

Online Publication Date: Oct 2009

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I was recently directed to an article on electric motorcycles in the Sept./Oct. online edition of Technology Review. Technology Review has particularly welcome articles on energy technologies—a topic that should be of interest to us all, and one of considerable interest to the U.S. federal government. I believe that with recent initiatives, the U.S. Department of Energy, led by Secretary of Energy Dr. Steven Chu (Nobel laureate in physics, 1997) now has the largest science research budget on our planet. Wonderful science is happening in the field of energy technology; and these efforts are well overdue.
Show PACS
01.50.H- Computers in education
01.30.Xx Publications in electronic media
89.20.Bb Industrial and technological research and development

Sixty Symbols, by The University of Nottingham

Dan MacIsaac, Column Editor

The Physics Teacher -- November 2009 -- Volume 47, Issue 8, pp. 556

Online Publication Date: Oct 2009

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Faculty at the University of Nottingham are continuing to develop short (5–10 minutes long) insightful video-streamed vignettes for the web. Their earlier sites: Test Tube: Behind the World of Science and the widely known Periodic Table of Videos (a video on each element in the periodic table featured in WebSights last semester) have been joined by a new effort from the faculty of Physics, Astronomy and Engineering—Sixty Symbols: Videos about the Symbols of Physics and Astronomy. I liked the vignette on chi myself.
Show PACS
01.50.H- Computers in education
01.30.Xx Publications in electronic media

Synchronous and Asynchronous Motors: Rotating Electric Fields

Dan MacIsaac, Column Editor

The Physics Teacher -- November 2009 -- Volume 47, Issue 8, pp. 556

Online Publication Date: Oct 2009

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by Sandro Ronca of the Italian Electrotechnical Association Direct link: http://tinyurl.com/y88uxtk Google translated URL (from Italian): http://tinyurl.com/ya54ezc
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01.50.H- Computers in education
01.30.Xx Publications in electronic media
84.50.+d Electric motors
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Physics for Teachers: Understanding Physics: David Cassidy, Gerald Holton, & James Rutherford

John L. Hubisz, Column Editor

The Physics Teacher -- November 2009 -- Volume 47, Issue 8, pp. 557

Online Publication Date: Oct 2009

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Physics for Teachers: Understanding Physics, by David Cassidy, Gerald Holton, & James Rutherford and published by Springer Verlag, New York, NY 10010 (2002), pp. xxiii + 851 $80.00 hardback. ISBN 0-387-98756-8. Student Guide & Instructor Guide are also available. The text and Instructor Guide are available online at http://www.dcassidybooks.com/up.html
Show PACS
01.30.Vv Book reviews
01.40.J- Teacher training
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