Classical applications of the Klein-Gordon equation

The quantum mechanical origin of the Klein-Gordon equation hides its capability to model many classical systems. We consider three examples of vibrating systems whose mathematical descriptions lead to the Klein-Gordon equation. These examples are adapted to applications such as the motion of suspended cables and Inca rope suspension bridges. We also discuss the correspondence between the classical and quantum settings of this equation as a way to provide an explanation of the concept of mass. (C) 2011 American Association of Physics Teachers. [DOI: 10.1119/1.3559500]