The physics of articulated toys—a jumping and rotating kangaroo

We describe the physics of an articulated toy with an internal source of energy provided by a spiral spring. The toy is a funny low cost kangaroo which jumps and rotates. The study consists of mechanical and thermodynamical analyses that make use of the Newton and centre of mass equations, the rotational equations and the first law of thermodynamics. This amazing toy provides a nice demonstrative example of how new physics insights can be brought about when links with thermodynamics are established in the study of mechanical systems.