1. INTRODUCTION. Physics often provides mathematics not only with a problem, but also with the idea of a solution. Physical reasoning has traditionally been a fruitful source of mathematical invention, having played a key role in some of the main discoveries of Archimedes, Bernoulli, and Riemann, among many others. In this article we give a much more modest example of a mathematical result that the author has discovered by means of a physical argument. We will also provide a one-paragraph physical proof of Ceva's theorem used in the discussion (and stated as Theorem 6).