Teaching Introductory Physics

by

Arnold B. Arons

(John Wiley and Sons, NY, 1997)

Edward F. Redish, University of Maryland, USA

One of the important tasks of a physics teacher is to help inspire a new crop of students to become physicists. In my personal trek towards becoming a professional physicist, I was lucky to have a young, inspiring high school teacher named Richard Powell. Later, I had the opportunity to work with and take courses with distinguished and well known physicists such as John Wheeler and Francis Low. My interactions with teachers provided formative highlights that helped both to develop my view of what physics is and the best ways to teach it. But today is not yesterday (it never is), and creating new physicists is turning into a much smaller (though still important) part of a physics instructor's responsibilities. Those of us in college and university physics departments need to significantly rethink our teaching as a result of the rapid expansion of the technological workplace and the growing need for workers and voters with a good understanding of science and technology. We must take on the responsibility of helping a large fraction of our students actually learn to use physics and understand physics in the highly restrictive context of their introductory physics course. For many of our students, that will be the only physics they ever choose to take. This makes our task much more difficult than when we could assume they would see the material again and again, and eventually understand physics when they came to teach it.

Fortunately, there are some tools that can provide valuable assistance. For decades, Arnold Arons has been helping physics teachers understand their students through insightful articles in journals such as The American Journal of Physics, The Physics Teacher, and Daedulus. With the publication of Teaching Introductory Physics by John Wiley and Sons, we have gained a tool for teachers of great and lasting value. The book consists of three parts. The first is a reprinting (with small corrections) of A Guide to Introductory Physics Teaching, Arons' 1990 volume that became an immediate classic. When it came out, I purchased a half a dozen copies and have been giving them to my Ph.D. students in physics education as an introduction to reflective teaching. It contains the distilled essence of 30 years of experience of a thoughtful and skilled teacher - one who listens carefully to his students and works to understand their difficulties. This part of the book is filled with surprising insights. (Try asking your introductory physics students whether an irregularly shaped object can have a well defined area. The results may surprise you.) It really becomes valuable when you realize that in rethinking your students' understanding of basic physics you are rethinking your own. The book contains many small subtle surprises and puzzles that delight, inform, and deepen one's understanding of introductory physics.

A useful aspect of this book for physics education researchers is that it includes many observations and comments that could be used as the start of a physics education research project. Observations such as Arons' are useful, but often benefit from more detailed documentation. For example, when A Guide to Introductory Physics Teaching appeared, I read that "Students should be led to try the effects of magnets on their Scotch Tape® electroscopes and to ascertain that there is no interaction … This paves the way for eliminating misconceptions such as repulsion between a north magnetic pole and a positive electric charge, and so on." I did not take much note of it. Later, I heard a report from the Physics Education Group at the University of Washington on a study of engineering students' responses to being taught about magnets.1 They found that upon entry over 80% of their students confused electric charges and magnetic poles. After a traditional instruction, this number remained above 50%. I was both flabbergasted and distressed at hearing this. I have taught that subject off and on for over 25 years. Furthermore, I believed that I listen carefully to students and I am sensitive to the issue that students bring previous knowledge into their classroom. Yet I had never imagined such a confusion was common. Needless to say, I probed my class upon my return and found exactly the same results as the Washington group. Arons' book does contain many references to the research literature where some of his observations are documented, but the list is not intended to be complete.

An aspect of Arons' book that makes it both enlightening and enjoyable is his deep and abiding interest in the process of science - how it evolves as well as how students can begin to understand "how do we know … why do we believe … ?" He fills the book with philosophical and historical insights. The final chapters of part I on "Achieving Wider Scientific Literacy" and "Critical Thinking" are provocative and insightful. I consider them to be among the best essays ever written on the subjects.

The book's Part II has also been previously published as Homework and Test Questions for Introductory Physics Teaching. It presents more than 400 thought-provoking conceptually challenging problems in introductory physics. I have used them as starting points for building supplementary homework and exam problems for my classes since the book first appeared in 1994 and have been very pleased with the results. However, the casual user should note that the problems are sometimes worded in Arons' characteristic eloquent style. I find that for my classes I often have to rewrite them using simpler vocabulary and shorter sentences. Also, many students will not like them! These problems require that the student actually think about the physics. In my experience, many students would prefer to do an hour of mindless plug-and-chug to ten minutes of thinking. When used with care and persistence, these problems can be used as part of a consistent effort to introduce beginning students to the joy of figuring things out. The paperback version of Part II could be used as a supplement to a traditional textbook.

The third part of the book is the only part that is truly new. Part III is a 150-page monograph on teaching the subject of energy. It assumes that the reader has a well-developed understanding of the concepts of force and Newton's laws, and has mastered the basic elements of calculus. It is therefore more appropriately a guide for the teacher. (Even if you wanted your students to use it you would have trouble. Wiley has unfortunately made the decision not to publish this part separately, so it can only be purchased together with the teacher's guide in part I - not something a teacher could easily require students to purchase.) Arons carefully analyzes the concepts of energy and points out many subtleties with care and clarity. A number of activities are presented in a way that can conveniently be adapted to serve a labs or extended class discussions.

As is typical with Arons, however, much of the material in part III has "some assembly required". This is not an "off-the-shelf' cookbook of lessons. Just as he requires his students build the concepts of physics for themselves, he implicitly expects his physics teachers to construct lessons and activities for their students for themselves, with helpful guidance from his materials. All in all, this volume is probably the best introduction to physics teaching available. I strongly recommend it to every teacher of introductory physics.

(Some sample problems from the book are on page 5. All

quotes used with permission.)
 

1 P. A. Krause, P. S. Shaffer, and L C. McDermott, "Using research on student understanding to guide curriculum development: An example from electricity and magnetism", AAPT Announcer 25 (Dec., 1995) 77.