Author, Reviewer Play Ball

It may not be good form for authors to respond to reviews of their books—but forbearance has its limits. In his review of my book The Science of Soccer (Physics Today, June 2003, page 64 ), John D. McCullen says that I give an “extraordinary incorrect” account of the bounce of the ball. In fact, my description is perfectly good physics. In a nutshell, here it is.

One can simply say that, during the bounce, the force on the ball is the reaction force from the ground to the equal air-pressure force on the contact area. Alternatively, one can correctly say that the total force on the casing of the ball in contact with the ground is zero (it is not accelerating), and in this description the force on the casing is the unbalanced pressure force on that part of the upper surface opposite to the part of the casing in contact with the ground. In the book, I give both descriptions. Each has its merits and both, of course, give the same correct answer.

A full account of the dynamics is given in the book, the first chapter of which is devoted to the ball and the bounce.