Duke engineering professor analyzes the physics of the Olympics

"Watching physics at the Olympics," a short article by Dr. Adrian Bejan, made me wish the author had been my high school physics teacher, because he makes the subject fun, interesting and instructive.

The article, which appears in the August issue of Academia Letters, analyzes the Olympics soccer competition and 100-meter sprint as live examples of fundamental physics.

Bejan teaches thermodynamics at Duke University, where he is the J.A. Jones Distinguished Professor of Mechanical Engineering.

He views soccer as a metaphor for individuals moving in society, where "change, evolution and organization come hand-in-glove with diversity and chance."

"Soccer is a live flow system," Bejan writes. He describes the ball as flowing from any point in the pitch to the goal, in channels that are "constantly morphing." One team (the offense) attempts to open up the channels while the other team (the defense) attempts to shut them down.

Bejan presents the playing field as a tree canopy, where the goal represents the base of the trunk and the channels of play, large and small, cover the canopy. The better players who control the ball more often fill the large channels that flow from the canopy to the goal. Supporting players fill the smaller channels that populate the canopy. 

The flowing tree image, he says, "is the icon of nature, animate and inanimate, from river basins and deltas to lungs, vascular tissues, air traffic and the spreading of news and viruses."

But don't focus on the soccer unpredictability, Bejan says, or you'll miss the physics "movie plot."

Predicting the 100-meter winner

Bejan's treatment of the 100m sprint considers the physics of locomotion and his method of predicting winners. The traditional theory is that taller winners (L) require fewer steps (N) than the shorter winners to reach the finish line. 

This might be a broadly correct prediction, Bejan says, but then how do you explain the "significant range of diversity [in steps] among the fastest"? He writes: "I realized that size is not the only feature of freedom that can be changed in order to witness a faster runner."

"The individual runner is stuck with his or her size L," he says. But with proper training, the runner can change the ratio of size to the step length. 

Bejan presents a table showing the height versus steps for six past champions and outlines future expectations: 

"There are two paths to winning medals. Taller runners gain an advantage from height. Shorter runners gain an advantage from making longer steps relative to their height. This holds equally for men and women."

In summary, Bejan uses the observable play of soccer and sprinting to make physics "palpable." He affirms that "athletics are contributing greatly to the teaching of physics and the spreading of freedom, peace, understanding and hierarchy (merit) on the globe."