Physics Around Us: How and Why Things Work,

Ernest M.
Henley
and
J. Gregory
Dash
,
World Scientific
, Hackensack, NJ, 2012. $34.00 (384 pp.). ISBN 978-981-4350-63-1

The Transition School at the University of Washington each year offers courses to as many as 16 talented middle school students to prepare them for direct entry into university classes. Among those offerings is a one-year, algebra-based, introductory physics course that was taught by Ernest Henley and the late J. Gregory Dash. The contents of that course now appear as a short textbook, Physics Around Us: How and Why Things Work.

When compared with most introductory texts covering the same subject, Physics Around Us has two big pluses: Listed at $34, it is cheap; coming in under 400 pages, it is short. The widely used algebra-based text College Physics (eighth edition, Brooks/Cole, 2009) by Raymond Serway, Chris Vuille, and Jerry Faughn is more than 1100 pages long and is listed at $285. A large market probably exists for short, inexpensive textbooks such as Physics Around Us.

Unfortunately, though, as much as I wanted to like the book, I cannot recommend it. Physics Around Us has a lot of errors. Most of them are small, but they are troublesome nonetheless. The worst error appears early in the book, on pages 47–48, in the discussion of an object falling through a fluid. The authors write, “A falling body is acted on by both gravity and air resistance, so the acceleration a is given by ma = mgkv. Since v = at, we have: ma = mgkat.”

As Physics Today readers will realize, that is wrong. The authors assume a formula for velocity that is correct only for constant-acceleration motion. They use the incorrect expression for velocity to derive an incorrect formula for acceleration as a function of time. I realize that the textbook is for students who haven’t taken calculus, but it would be much better to simply state the correct result without proof than to use faulty mathematics to get the wrong one.

In the same discussion, the authors state that at very low speeds, the resistance of an object in a fluid is proportional to the velocity. That is the form of drag force that they consider in the text. While that is true in the low Reynolds number regime, in most real-world cases the drag force is proportional to velocity squared. If you take that more realistic approach, you can derive the correct expression for terminal velocity without using calculus by equating the drag force with the weight of the falling body. The bonus is that it also shows how terminal velocity depends on fluid density, mass, and surface area. There’s a lot more physics in that approach than the approach taken by the authors.

Space prevents me from discussing all the errors, but there are enough that I would think twice before using the book. Examples of simple mistakes include incorrect values listed for the lowest temperature ever achieved and for the proton-to-electron mass ratio. Two other issues are that many of the qualitative questions are poorly worded and their sample solutions are sometimes wrong or highly misleading. Those errors point to a lack of attention to detail and to poor editing.

After reading the book, I got a new appreciation for just how well written and well edited the large, expensive textbooks are. Yes, the prices are high, but you’re paying for the work of authors vetted by a large publishing house and its problem writers, photographers, numerous editors, and several reviewers. But, you might say, $200 is a lot to spend on a textbook, no matter how well written. The teacher can do much to compensate for the problems with a book like Physics Around Us, so why not use it when cost is an issue?

There are better options. OpenStax College offers College Physics, a free online textbook at the same level; readers have the option to pay roughly $50 to get a bound copy. That book is 1270 pages long and devotes lots of space to real-world examples, problem-solving tactics, and links to Web-based applications. It also includes good illustrations. And the section on the drag force—or any other comparable section—is much better written and more accurate than the discussion in Physics Around Us. There is no question which book I would choose to use.