What can a physicist, or a golfer, learn from The Science of the Perfect Swing? We are cousins, co-writing this review; one of us, a physicist (C.F.), has never played a round of golf in his life; the other (R.F.) is a lifelong, passionate golfer. The book's title is a conscious reference to The Search for the Perfect Swing, a now-classic 1968 treatise on golf by Alistair Cochrane and John Stobbs, republished with minimal changes in 2005.
The author of The Science of the Perfect Swing, Peter Dewhurst, has had a distinguished career as both an industry and university researcher, focusing on various topics in aerospace and mechanical engineering, and most recently on sports and sports equipment. Currently, he is Professor Emeritus in the Department of Mechanical, Industrial, and Systems Engineering at the University of Rhode Island. Among other honors during his career, he was awarded the presidential National Medal of Technology and Innovation in 1991.
Dewhurst's book has seven chapters, an introductory chapter followed by chapters on ball flight (effects of air drag, ball spin, headwinds, and tailwinds on trajectory), ball striking (club speed, contact time, loft), the generation of ball spin, the rules for curved ball flight (effects of off-axis spin on hooks and slices), driver impact and ball flight (club design, off-center strikes), and putting. Each chapter is separated into two sections, the first “written in a descriptive style devoid of the jargon and abbreviations of science.” These first sections employ golfer-familiar units like miles per hour, yards, and pounds so as to “relate directly to golf commentary, to the general golf literature, and to everyday experience [for Americans] in a range of other activities.” The second sections of chapters lay out “the more complex derivations of the scientific models of the different aspects of the game” and employ metric units to “allow the scrutiny of the scientific community.”
This book is aimed at readers with at least some knowledge of physics or engineering. Even the “descriptive” chapter sections use terms like coefficient of restitution and moment of inertia, which, although explained briefly in the introduction, are likely to be daunting to golfers with a high-handicap knowledge of mechanics. Even first- and second-year undergraduate physics and engineering majors probably won't find this book accessible.
So, what did we learn from this book? Our non-golfing reviewer was intrigued to learn that the widely advertised Big Bertha-style clubs—with a huge, hollow club head and a thin, titanium face where ball and club meet—really are a great investment. They do drive the ball farther than smaller, old-style, solid wood clubs, and their superiority holds both for the professional-level golfer and the weekend duffer. They are superior because a bigger, hollow club has a larger moment of inertia, reducing energy lost in club twisting after slightly off-center hits, and because the thickness/flexibility of the titanium face is designed to match the elastic properties of golf balls, thus increasing the coefficient of restitution of the collision (i.e., the “trampoline effect”).
Our non-golfing reviewer was also surprised at just how much influence a golfer has on the spin of the golf ball. When a ball is struck with a club having an upward-angled face, the ball acquires backspin. The “velocity spin coefficient of restitution” (SCoR) may range from minus one (frictionless sliding, or no spin), zero (rolling without slipping, or backspin), or positive (overspin, i.e., even more backspin than rolling without slipping). In practice, SCoR depends on the choice of ball and club, as well the presence of grass or dirt on their surfaces (that's why, just before striking the ball, golfers sometimes clean ball and club). For long drives golfers want some backspin (SCoR ∼–0.3) to provide lift during flight, but not too much because that reduces the distance added when the ball lands, bounces, and rolls. For shorter chip shots, extra backspin (SCoR ∼ +0.30 to +0.38) helps to stop the ball when it contacts the green. In all phases of the game, creating/controlling this back/overspin has important implications, because spin significantly affects the ball's trajectory both during flight and after it lands.
If you are a golfer, this book could affect your decisions about what equipment to purchase, but don't buy it if you want practical advice to improve your game. There is nothing about the biomechanics of the human body during the golf swing, no hints about how to practice, nothing about strategy, and no diagrams of golf courses or particular holes, famous or otherwise, with insights about how best to play them. In all these respects, The Science of the Perfect Swing is the exact opposite of its 1968 referent, The Search for the Perfect Swing, which offered copious practical advice for golfers.
However, you should definitely acquire this book if you dream of designing golf clubs or other golf equipment, or if you wanted to develop computer models of golf. The book presents a wealth of experimental data about how different equipment and striking parameters affect distance and spin. It includes essential analytical equations describing the physics of ball flight and ball-club interaction. And because most of these equations are highly nonlinear and not solvable analytically under real-life conditions, it also includes numerous rule-of-thumb equations for estimating distance or spin in situations a golfer might encounter in practice. The Science of the Perfect Swing's single-minded focus on the interaction between golf club and golf ball, while excluding practical and cultural elements of the game, is similar to Rod Cross's treatise on the baseball and bat, Physics of Baseball and Softball (Springer, 2011).
So, is The Science of the Perfect Swing for you? One of our daughters said it best when she was a freshman in college. That year she took introductory courses in earth science and in psychology. Both subjects were interesting, she said, but in earth science she found there was too much “needless detail” whereas psychology was, well, just plain interesting. Today she is a clinical psychologist.
Whether or not you like Peter Dewhurst's book will depend on just exactly how much detail you find interesting, or needless, on the mechanics of clubbing a golf ball. The book has no fewer than 172 graphs and line drawings and 49 tables. It has no photographs (zero). And in 271 pages it never once mentions Tiger Woods, Arnold Palmer, Jack Nicklaus, or Bobby Jones. But, if you need detailed information about what happens when ball meets club, this book is for you.
Cliff Frohlich, a research scientist at the University of Texas at Austin, is an earthquake seismologist who has published seven articles on the physics of sports in the American Journal of Physics. Rich Frohlich is a mechanical engineer employed by Associated Aerospace Activities, Inc. in San Leandro, California.
