Selective suppression of normal modes in coupled oscillators

In this paper we present experimentally and discuss quantitatively two experiments, in which we show how to suppress in turn selectively one of the two normal modes of a system made of two oscillators (each consisting of a cart and a spring), mutually coupled by an interaction spring. This way, while friction is usually considered an undesirable side effect, the role of dissipation is highlighted. We also discuss, from a didactic perspective, how the experiments presented can be useful to introduce fundamental physical concepts and processes.