Football Physics : The Science of the Game , by Timothy Gay, Ph.D.

Book Review

Dr. Timothy Gay, of the physics department at the University of Nebraska, also played football at Caltech, and has worked as a football team manager.

In his new book, Football Physics , he writes, "As manager, I got to see what goes on goes on behind the scenes for a football team to be successful. As a science geek, I was particularly interested in the technical aspects...." [xi]

Chapter 1 provides perfectly clear (and perfectly correct) descriptions of the physics concepts of velocity, acceleration, mass, force, momentum, impulse, and Newton's Laws. The text moves along quickly to the more abstract concepts of the collision and the center of mass. All of these ideas are explained in the context of the football maneuver which Vince Lombardi is quoted [18] as considering the most important of all -- and the title of the first chapter -- Blocking and Tackling.

Chapter 2 elaborates on these principles by introducing the ideas of power and kinetic energy. The author begins to move beyond the subject of blocking and tackling, while returning as needed.

In Chapter 3, the tactic called the West Coast Offense gives the author the occasion to introduce physics in two dimensions and the idea of vectors.

Chapter 4, The Football in Flight, looks in detail at the the trajectory of a football when it is thrown, kicked or punted. This arched path is the parabola. Gravity is the main force at work, but not the only one. Since temperature and humidity affect the range and hang time, the author introduces the reader to the ideal gas law and the Kelvin scale.

About the Author

Timothy Gay, Ph.D., has been a professor of physics at the University of Nebraska-Lincoln since 1993. Dr. Gay currently heads a research group that is funded by the National Science Foundation. He lives in Lincoln, Nebraska.

- From the Publisher

Chapter 5, Kicking, is the longest chapter in the book. When torque is applied during a kick, the pivot point is the kicker's hip joint [135], in addition to the knee joint when the lower leg is whipped [139]. The author here explains the angular (rotational) forms of velocity, acceleration, and kinetic energy. Since the motion is rotational, the idea of mass, as the property that makes object resist being accelerated, must be replaced by the slightly more complex idea of the moment of intertia.

In an elastic collision, there is conservation of both momentum and energy. There is a return to the concept of impulse, which was introduced in chapter 1, while considering a photograph of a football which has a deformed shape while the foot is in contact with it for 8 milliseconds. [143] Conservation of linear momentum governs the collision. Conservation of angular momentum is also observed, as when the kicked ball tumbles around its center of mass. [144-145]

The chapter on kicking briefly mentions the concept of frame of reference. [135]

To clarify the idea of air drag, Dr. Gay compares two record-breaking field goals, one performed by Tom Dempsey in New Orleans (approximately at sea level) and one by Jason Elam at the Mile High Stadium. [139-142]

The author points out a several causal relations which some may find unexpected. For example, "If our kicker puts the arc of his foot right through the ball's center of mass, he won't exert any torque on it to make it tumble. You might think that this will make the ball go faster, but it won't." [146] Another counterintuitive issue is related to the fact that the punter wants to maximize the ball's hang time. Dr. Gay begins, "The first question we want to ask is: When does a field-goal situation become a punting situation?" [148] He illustrates scientifically that "maximum hang time is not compatible with maximum range." [148]

Although not the author's main intention, the section entitled Kicking Strategy gives the reader a little introduction to the skill of analyzing trends in data. A multilevel bar chart illustrates the percentages of attempted and successful field goal kicks as a function of range or "yardage." [149]

The author poses an interesting what-if. Since the time that the ball "hangs" in the air is so significant in football, what would happen if we were to fill the ball with helium? The result isn't what you might expect. Hint: we would still be required to pump the gas to the same pressure required by NFL rules. The staff of Sports Illustrated magazine tried this experiment, and the book compares the results of their experiment to the prediction made by the Ideal Gas Law.

Chapter 6, Passing the Football, reminds us that accuracy and range are not the only important factors; the speed is also important to minimize the chance of interception. We can see why the ball behaves differently for the motion of a quarterback than it would for the type of motion used by a soccer goalie. [169] We need to consider the ball's motion other than its translation through the air -- we also have to consider its spiraling, tumbling and wobbling. [171] To understand these components of motion, we look more closely at angular momentum and drag. [181]

Chapter 7, Gear, offers a scientific look at the chatacteristics of the balls, helmets, pads, etc.

In Chapter 8, Turf, we see some of the considerations that have become important in football since domed stadiums with artificial grass made their first appearance in the 1960s. There are several kinds of friction. Static friction and sliding friction have different values for the property known as the coefficient of friction. The resilience or springiness of the grass is also crucial. When a running back makes a "cut", the full weight of the body is momentarily placed on one foot. [235] Cleat length also affects the coefficient of friction for both the cases of grass and Astroturf. Such bodily injuries as "turf burn" can be easily understood. [237] We can also see why softer or wet grass reduces the distance that a ball rolls on the ground. [241]

Chapter 9, Waves in the Stadium considers the "Wave" in addition to the original kind of wave, such as the sounds we hear. Dr. Gay writes a fascinating and original discussion the popular Wave in terms of the theories of the behavior of people in crowds. What determines the probability of a person will do something, given that the person already sees another person doing the same thing? That's a question that has entertained those who think about such diverse subjects as popular culture and politics.

Science enthusiasts will require no convincing to see the value of Football Physics . Those who enjoy science, and especially those who teach it, are always on the lookout for examples from everyday life that illustrate basic principles, hence they use such common household objects as seesaws, wheelbarrows and nutcrackers to explicate the principles in the Newtonian mechanics unit. The author expertly describes a popular sport in these physical terms. He is quite skilled at combining common sense and technical accuracy.

Likewise, a football player or fan will enjoy and benefit from this new book. It's a lower level of appreciation to say that a particular maneuver or tactic is used in the game merely because the player has been accustomed or trained to do it in such a circumstance. It is a much deeper kind of appreciation to understand why each play or strategy is chosen at a particular time, for a particular purpose, and to know how and why it works.

A major contribution to science and sports literature, Football Physics is a book that deserves to soar upward on the bestseller lists for both subjects.

Book review by Mike Lepore for crimsonbird.com

9 chapters plus appendices. Black & white illustrations. 12-page index.