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Apr 2010

Volume 48, Issue 4, pp. 212-272

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Second chances for students

Jay M. Pasachoff, Field Memorial Professor of Astronomy, Director, Hopkins Observatory

The Physics Teacher -- April 2010 -- Volume 48, Issue 4, pp. 212

Online Publication Date: Mar 2010

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01.40.gb Teaching methods and strategies
01.50.Kw Techniques of testing

Authors' response

Charles Henderson and Kathleen Harper

The Physics Teacher -- April 2010 -- Volume 48, Issue 4, pp. 212

Online Publication Date: Mar 2010

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01.40.gb Teaching methods and strategies
01.40.gf Theory of testing and techniques

A comment regarding the Coriolis effect

N. Gauthier, Professor Emeritus

The Physics Teacher -- April 2010 -- Volume 48, Issue 4, pp. 212

Online Publication Date: Mar 2010

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Abstract Unavailable
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01.40.gf Theory of testing and techniques
01.55.+b General physics
01.50.Rt Physics tournaments and contests

Hewitt's response

Paul G. Hewitt

The Physics Teacher -- April 2010 -- Volume 48, Issue 4, pp. 212

Online Publication Date: Mar 2010

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01.40.gf Theory of testing and techniques
01.55.+b General physics
01.50.Rt Physics tournaments and contests
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A physics teacher goes to Washington

Brian A. Pyper

The Physics Teacher -- April 2010 -- Volume 48, Issue 4, pp. 214

Online Publication Date: Mar 2010

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01.10.Hx Physics organizational activities
01.60.+q Biographies, tributes, personal notes, and obituaries
01.85.+f Careers in physics and science
01.78.+p Science and government (funding, politics, etc.)
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POLAROIDS

Paul Hewitt

The Physics Teacher -- April 2010 -- Volume 48, Issue 4, pp. 216

Online Publication Date: Mar 2010

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01.40.gf Theory of testing and techniques
01.50.Kw Techniques of testing
01.50.Rt Physics tournaments and contests
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Teaching the Fundamentals of Cell Phones and Wireless Communications

Mark Davids, Rick Forrest, and Don Pata

The Physics Teacher -- April 2010 -- Volume 48, Issue 4, pp. 217

Online Publication Date: Mar 2010

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Wireless communications are ubiquitous. Students and teachers use iPhones®, BlackBerrys®, and other smart phones at home and at work. More than 275 million Americans had cell phones in June of 20091 and expanded access to broadband is predicted this year.2 Despite the plethora of users, most students and teachers do not understand “how they work.” Over the past several years, three high school teachers have collaborated with engineers at Cingular, Motorola, and the University of Michigan to explore the underlying science and design a three‐week, student‐centered unit with a constructivist pedagogy consistent with the “Modeling in Physics” philosophy.3 This unique pilot program reinforces traditional physics topics including vibrations and waves, sound, light, electricity and magnetism, and also introduces key concepts in communications and information theory. This article will describe the motivation for our work, outline a few key concepts with the corresponding student activities, and provide a summary of the program that has been developed to engage and inspire the next generation of scientists, engineers, and citizens.
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01.40.gb Teaching methods and strategies
84.40.Ua Telecommunications: signal transmission and processing; communication satellites
85.30.-z Semiconductor devices
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Bola Motion

Thomas McCarthy

The Physics Teacher -- April 2010 -- Volume 48, Issue 4, pp. 222

Online Publication Date: Mar 2010

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Toward the end of the AP® Physics C Mechanics course, I challenge my students to integrate many of the concepts they have learned in both the classroom and laboratory by completing the “Bola Lab.” The title is based on the Argentinean gaucho (cowboy) herding tool, the boleadora, or bola for short (see Fig. 1),1 which consists of two heavier weights attached to two longer cords and a lighter weight attached to a shorter cord, as shown in Fig. 2.2 The bola is held by the smaller ball and twirled in a horizontal plane around the head to give the balls momentum and then released. Being thrown in this manner arranges the two heavier weights to rotate and fly closer together as compared with a bola with equal weights and cord lengths.3 With practice, this will result in the pair hitting either side of the cattie's legs, and the lighter weight then swings around this instantaneous axis of rotation, thus wrapping up the animal's legs4,5 and capturing him. The weights are chosen so they do not harm but merely capture the animal.
Show PACS
01.40.gb Teaching methods and strategies
01.55.+b General physics
01.50.Pa Laboratory experiments and apparatus

Teaching Physics Using PhET Simulations

C. E. Wieman, W. K. Adams, P. Loeblein, and K. K. Perkins

The Physics Teacher -- April 2010 -- Volume 48, Issue 4, pp. 225 | Cited 2 times

Online Publication Date: Mar 2010

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PhET Interactive Simulations (sims) are now being widely used in teaching physics and chemistry. Sims can be used in many different educational settings, including lecture, individual or small group inquiry activities, homework, and lab. Here we will highlight a few ways to use them in teaching, based on our research1 and experiences using them in high school and college classes. On our website we have a more complete guide to using PhET sims in the classroom: phet.colorado.edu/teacher_ideas/classroom‐use.php.
Show PACS
01.40.gb Teaching methods and strategies
01.50.H- Computers in education
01.40.J- Teacher training
FREE

Women and Men of the Manhattan Project

Jill Marshall, Caroline Herzenberg, Ruth Howes, Ellen Weaver, and Dorothy Gans

The Physics Teacher -- April 2010 -- Volume 48, Issue 4, pp. 228 | Cited 2 times

Online Publication Date: Mar 2010

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In the early 1990s Ruth Howes, a nuclear physicist on the faculty at Ball State University, and Caroline Herzenberg, a nuclear physicist at Argonne National Laboratory, were asked to write a chapter on the Manhattan Project for a volume on women working on weapons development for the military.1 Realizing that they knew very little about the women who had been involved in that effort, they embarked on a mission to find out more. Howes and Herzenberg were able to document the wartime contributions of more than 1000 women in Their Day in the Sun,2 preserving this legacy for generations to come. At the 2009 AAPT Winter Meeting in Chicago, the AAPT Committee on Women in Physics celebrated the accomplishments of these women and the men who worked beside them in a session co‐sponsored with the History and Philosophy of Physics and the Concerns of Senior Physicists committees. Howes presented an overview of the contributions of women to the development of the first nuclear weapon, and the session was honored with the presence of Manhattan Project veterans Ellen Cleminshaw Weaver, who worked at Oak Ridge, and Dorothy Marcus Gans, who worked as a technician in the Metallurgical Laboratory in Chicago.

Determination of the Specific Heat Ratio of a Gas in a Plastic Syringe

Jeff Chamberlain

The Physics Teacher -- April 2010 -- Volume 48, Issue 4, pp. 233

Online Publication Date: Mar 2010

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The rapid compression or expansion of a gas in a plastic syringe is a poor approximation of an adiabatic process. Heat exchange with the walls of the syringe brings the gas to equilibrium in an amount of time that is not significantly greater than the length of the compression or expansion itself. Despite this limitation, it is still possible to measure the pressure changes during a rapid change in volume and calculate an approximation of the pressures for an adiabatic process. From these values the specific heat ratio of the gas can be calculated.
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01.50.Pa Laboratory experiments and apparatus
01.40.gb Teaching methods and strategies

Assessment of a Solar System Walk

Michael C. LoPresto, Steven R. Murrell, and Brian Kirchner

The Physics Teacher -- April 2010 -- Volume 48, Issue 4, pp. 236 | Cited 1 time

Online Publication Date: Mar 2010

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The idea of sending students and the general public on a walk through a scale model of the solar system in an attempt to instill an appreciation of the relative scales of the sizes of the objects compared to the immense distances between them is certainly not new. A good number of such models exist, including one on the National Mall in Washington, D.C., starting at the Smithsonian Air and Space museum.1 A pioneering model and inspiration for our own is on the campus of the University of Colorado in Boulder,2 and there are others.3 Those at science museums are often used by the general public and field-trip groups, while the ones on college campuses are also used by students of introductory astronomy.
Show PACS
01.50.My Demonstration experiments and apparatus
01.40.gb Teaching methods and strategies
01.55.+b General physics

Reflection by Porro Prisms

Thomas B. Greenslade, Jr.

The Physics Teacher -- April 2010 -- Volume 48, Issue 4, pp. 240

Online Publication Date: Mar 2010

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Students all know that reflection from a plane mirror produces an image that is reversed right to left and so cannot be read by anyone but Leonardo da Vinci, who kept his notes in mirror writing. A useful counter‐example is the Porro prism, which produces an image that is not reversed.
Show PACS
01.50.My Demonstration experiments and apparatus
01.55.+b General physics
01.40.gb Teaching methods and strategies

Battleship Buoyancy

J. Patrick Dishaw

The Physics Teacher -- April 2010 -- Volume 48, Issue 4, pp. 242

Online Publication Date: Mar 2010

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One of the most dramatic demonstrations of the Archimedes principle is the simple fact that battleships float. I estimate the depth of a battleship in seawater as an example in my physics classes. I use the battleship Arizona as an exemplar of a class of U.S. battleships used during World War II. The Arizona was 608 ft (185.3 m) long and 97 ft 1 in (29.6 m) wide at its widest dimension. The unloaded weight of the ship was 31,400 U.S. tons (2.79× 108 N).1 How deep would the Arizona sink into seawater of density 1028 kg/m3?
Show PACS
01.50.-i Educational aids
01.40.gb Teaching methods and strategies
01.55.+b General physics

Modeling the Motion of an Increasing Mass System

William Kunkel and Randal Harrington

The Physics Teacher -- April 2010 -- Volume 48, Issue 4, pp. 243 | Cited 2 times

Online Publication Date: Mar 2010

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Problems on the dynamics of changing mass systems often call for the more general form of Newton's second law1 Fnet = math. These problems usually involve situations where the mass of the system decreases, such as in rocket propulsion. In contrast, this experiment examines a system where the mass increases at a constant rate and the net force remains constant. This system provides a context that is different, and in some ways simpler, than the rocket propulsion systems typically introduced in introductory courses.
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01.50.Pa Laboratory experiments and apparatus
01.40.gb Teaching methods and strategies

The Role of Sign in Students' Modeling of Scalar Equations

Kate Hayes and Michael C. Wittmann

The Physics Teacher -- April 2010 -- Volume 48, Issue 4, pp. 246 | Cited 2 times

Online Publication Date: Mar 2010

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Helping students set up equations is one of the major goals of teaching a course in physics that contains elements of problem solving. Students must take the stories we present, interpret them, and turn them into physics; from there, they must turn that physical, idealized story into mathematics. How they do so and what problems lie along the way are a major source of difficulty for us as instructors. In this paper, we consider just one such difficulty, getting the plus and minus signs correct when setting a net force equal to mass times acceleration. Even in such simple equations, we find that students make common errors in how they connect the mathematics and the physics. Specifically, we have seen college physics students use physical and mathematical reasoning inconsistently when determining signs of terms in equations. The problem seems to lie in how a vector equation gets interpreted into a scalar equation (whose form depends on one's choice of coordinate system).
Show PACS
01.40.gb Teaching methods and strategies
01.40.Ha Learning theory and science teaching

What Is the Best Launch Angle To Hit a Home Run?

David Kagan

The Physics Teacher -- April 2010 -- Volume 48, Issue 4, pp. 250 | Cited 1 time

Online Publication Date: Mar 2010

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Your students will proudly raise their hands and answer, “45 degrees!” They are, however, answering a different question. It is true that in the absence of air resistance, for a given initial speed, the launch angle that maximizes the range is 45°. For a real homer, there are many complicating factors that make the question far more challenging to answer. Here is a partial list: 1. The initial speed off the bat is not fixed. Garvey's law, “The harder you hit it, the further it goes” is definitely at play; 2. Air resistance is a substantial influence on the flight of the ball.1; 3. The backspin on a well‐hit ball creates lift due to the Magnus effect.2; 4. Atmospheric conditions such as humidity, temperature, air density, and the wind affect the motion as well.3; 5. Baseball parks are unique in size and shape. So, a home run in one park may not be a home run in another.
Show PACS
01.40.gb Teaching methods and strategies
01.40.gf Theory of testing and techniques
01.55.+b General physics

Need a Classroom Stimulus? Introduce Radio Astronomy

Samuel Derman

The Physics Teacher -- April 2010 -- Volume 48, Issue 4, pp. 251

Online Publication Date: Mar 2010

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Silently, invisibly, ceaselessly, our planet Earth is showered by radio waves from every direction and from every region of space. This radio energy originates in our solar system, throughout the Milky Way galaxy, and far beyond, out to the remotest reaches of the universe. Detecting and unraveling the origins of these invisible signals is what radio astronomy is all about. This ever‐present radiation provides astronomers with an alternate, non‐optical window to the universe, revealing exotic and unfamiliar phenomena previously undetected by even the most powerful optical telescopes. For physics teachers, a classroom discussion of these radio discoveries, however brief, offers an opportunity for igniting interest (and possibly a career option) in even the most apathetic of students. This paper describes, first, the background of some of these events, and second (in the appendixes), a selection of numerical problems so that students can derive for themselves the truly mind‐stretching features of these celestial objects.
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01.65.+g History of science
01.75.+m Science and society
01.40.Fk Research in physics education

Can We Trace Arbitrary Rays To Locate an Image Formed by a Thin Lens?

Decha Suppapittayaporn, Bhinyo Panijpan, and Narumon Emarat

The Physics Teacher -- April 2010 -- Volume 48, Issue 4, pp. 256

Online Publication Date: Mar 2010

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After learning how to trace the principal rays [Fig. 1(i)] through a thin lens in order to form the image in the conventional way, students sometimes ask whether it is possible to use other rays emanating from the object to form exactly the same image—for example, the two arbitrary rays shown in Fig. 1(ii). The answer is a definite yes, and this paper presents a method of doing so.
Show PACS
01.40.gb Teaching methods and strategies
01.55.+b General physics

Getting Rid of Gravity — Alternative Ways of Looking at Trajectories

Peter W. Dion and Anthony M. H. Ho

The Physics Teacher -- April 2010 -- Volume 48, Issue 4, pp. 258

Online Publication Date: Mar 2010

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Problems in projectile motion are a time-honored staple of high school and even first-year university physics. They can become confusing for some students, yet boring for the stronger students. Herein we present two alternative approaches to such questions, one we call “breaking down gravity,” which makes these questions easier to solve, and the other we call “getting rid of gravity,” which converts such questions into a more interesting and challenging form.
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01.40.gb Teaching methods and strategies
01.40.ek Secondary school

Instantaneous Velocity Using Photogate Timers

John Wolbeck

The Physics Teacher -- April 2010 -- Volume 48, Issue 4, pp. 262 | Cited 1 time

Online Publication Date: Mar 2010

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Photogate timers are commonly used in physics laboratories to determine the velocity of a passing object. In this application a card attached to a moving object breaks the beam of the photogate timer providing the time for the card to pass. The length L of the passing card can then be divided by this time to yield the average velocity (or speed) of the passing object: Vavg = L/t.
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01.50.Pa Laboratory experiments and apparatus
01.40.gb Teaching methods and strategies
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An apparatus to simulate an amusement park rotor

Carlos Saraiva

The Physics Teacher -- April 2010 -- Volume 48, Issue 4, pp. 265 | Cited 1 time

Online Publication Date: Mar 2010

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The rotor is a device that can be found in many amusement parks.1 In the literature there are various articles about this topic. The rotor is a hollow cylindrical room, covered inside with canvas and which can be rotated about the central vertical axis. People stand upright, with their backs against the internal face of the device. When it reaches a certain angular speed, the floor moves down and people don't fall; they are apparently stuck to the walls of the rotating cylinder.
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01.50.My Demonstration experiments and apparatus
01.40.gb Teaching methods and strategies
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Fermi Questions

Larry Weinstein, Column Editor

The Physics Teacher -- April 2010 -- Volume 48, Issue 4, pp. 266

Online Publication Date: Mar 2010

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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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Cat's Cradle

Boris Korsunsky, Column Editor

The Physics Teacher -- April 2010 -- Volume 48, Issue 4, pp. 267

Online Publication Date: Mar 2010

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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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Project YouTube

Diane Riendeau, Column Editor

The Physics Teacher -- April 2010 -- Volume 48, Issue 4, pp. 268

Online Publication Date: Mar 2010

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Thanks to Jim Hicks, Harrington High School (retired), Harrington, IL, for the numerous emails regarding this idea!
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01.50.F- Audio and visual aids
01.50.H- Computers in education
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Misconceptions as necessary stepping stones

Patricia Blanton, Column Editor

The Physics Teacher -- April 2010 -- Volume 48, Issue 4, pp. 269

Online Publication Date: Mar 2010

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I've been reading an online book called Ready, Set, Science! Putting Research to Work in K‐8 Science Classrooms (www.nap.edu/catalog.php?record_id=11882) and have found the discussion very enlightening. I think that any beginning science teacher might want to look at this book for guidance in designing lessons and managing student discussions to help students become more thoughtful, productive, and independent learners. While the book gives examples of K‐8 classrooms, the examples of classroom discourse could serve as a road map for teachers at any level who want to make their classrooms more student centered and a place where all learners are actively engaged.
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01.40.J- Teacher training
01.40.Ha Learning theory and science teaching
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Playing with refraction

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

The Physics Teacher -- April 2010 -- Volume 48, Issue 4, pp. 270

Online Publication Date: Mar 2010

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Abstract Unavailable
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01.50.My Demonstration experiments and apparatus
01.40.gb Teaching methods and strategies
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Teaching Physics with personal response systems or “clickers”

Dan MacIsaac, Column Editor

The Physics Teacher -- April 2010 -- Volume 48, Issue 4, pp. 271

Online Publication Date: Mar 2010

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Abstract Unavailable
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01.30.Xx Publications in electronic media
01.50.H- Computers in education

Einstein‐Online, a website about Einstein's theories of relativity, http://www.einstein‐online.info/

Stephanie Chasteen

The Physics Teacher -- April 2010 -- Volume 48, Issue 4, pp. 271

Online Publication Date: Mar 2010

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Abstract Unavailable
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01.30.Xx Publications in electronic media
01.50.H- Computers in education
01.40.J- Teacher training

NASA rocket disrupts a Sun dog, apod.nasa.gov/apod/ap100223.html

Brittni Barr

The Physics Teacher -- April 2010 -- Volume 48, Issue 4, pp. 271

Online Publication Date: Mar 2010

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Abstract Unavailable
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01.30.Xx Publications in electronic media
01.50.H- Computers in education

“Science Bag” from University of Wisconsin Milwaukee, www4.uwm.edu/letsci/sciencebag/videos/phys.cfm

Chris Chiaverina

The Physics Teacher -- April 2010 -- Volume 48, Issue 4, pp. 271

Online Publication Date: Mar 2010

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Abstract Unavailable
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01.30.Xx Publications in electronic media
01.50.H- Computers in education
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A Great Find! Eureka Man: The Life and Legacy of Archimedes: Alan Hirshfeld

John Boeder

The Physics Teacher -- April 2010 -- Volume 48, Issue 4, pp. 272

Online Publication Date: Mar 2010

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Abstract Unavailable
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01.30.Vv Book reviews
01.65.+g History of science
01.60.+q Biographies, tributes, personal notes, and obituaries

MicroReviews by the Book Review Editor: Study Skills: A Student Survival Guide: Kathryn L. Allen

John L. Hubisz, Column Editor

The Physics Teacher -- April 2010 -- Volume 48, Issue 4, pp. 272

Online Publication Date: Mar 2010

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Abstract Unavailable
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01.30.Vv Book reviews
01.40.Ha Learning theory and science teaching

MicroReviews by the Book Review Editor: Walking Zero: Discovering Cosmic Space and Time along the Prime Meridian: Chet Raymo

John L. Hubisz, Column Editor

The Physics Teacher -- April 2010 -- Volume 48, Issue 4, pp. 272

Online Publication Date: Mar 2010

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Abstract Unavailable
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01.30.Vv Book reviews
01.70.+w Philosophy of science

MicroReviews by the Book Review Editor: Electricity and Magnetism: A Historical Perspective: Brian Baigrie

John L. Hubisz, Column Editor

The Physics Teacher -- April 2010 -- Volume 48, Issue 4, pp. 272

Online Publication Date: Mar 2010

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Abstract Unavailable
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01.30.Vv Book reviews
01.65.+g History of science
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