Can a Bicycle Create a Unicycle Track?
David L. Finn · College Mathematics Journal · 2002
In the Sherlock Holmes mystery “The Priory School,” a telling piece of evidence comes from the observation and ensuing analysis of a pair of tire tracks. This evidence led Holmes and Watson to discover the murder of a school master, and subsequently to discover the identity of a Duke’s son. The critical part of the analysis is Holmes’ argument that the direction a bicycle was traveling can be determined by using the indentation of the tire tracks at a crossing to determine which track was created by the back tire. Once this is known, the direction the bicycle was travelling can be determined by the orientation of the treads of the back tire. Problems have been noted with Holmes’ argument (see [9]). However, there are other methods for determining the direction a bicycle was travelling. For instance, in the solution to the title problem of the book Which way did the bicycle go? [9], the authors show how the direction a bicycle is traveling can be determined using a simple calculus argument.