A simulation of the Tacoma narrows bridge oscillations

The famous collapse of the Tacoma Narrows Bridge in November of 1940 has been a topic of lively discussion ever since. The reasons for the collapse are complex, and in the past it has been treated as a case of destructive resonance and more recently as a case of aerodynamic self-excitation. We have developed a very simple real-time demonstration using a box supported with rubber bands and a fan that clearly shows how large oscillations can be generated in an unstable object with a simple air source.