A Simple Classroom Double Pendulum

In this article, we construct a very simple double pendulum (the concept of a pendulum should be familiar to all beginning students of classical mechanics). Since a double pendulum has two degrees of freedom, we suggest that this pendulum can be used in the classroom environment to illustrate the concept of normal modes, and we use video software to show that it is possible to observe a normal mode in action. The pendulum as we describe it should be constructable by all students and is much simpler than the similar experimental setups described in the literature.