What to Say About the Tacoma Narrows Bridge to Your Introductory Physics Class

Having just taught my introductory physics class about the collapse of the Tacoma Narrows Bridge, I realized that this topic is fascinating both to the students and to me. I always show the video and it never fails to elicit numerous questions from the class. However, its treatment in most introductory physics textbooks is either at best inadequate or at worst misleading. By chance, I also recently heard a talk from the project manager of a proposed new bridge across the Mississippi River at St. Louis. The issues that led to the failure of the Tacoma Narrows Bridge played a major role in the design of this new bridge. These two events have led me to think about the physics of bridge oscillations and to write this paper, which is in large part an abridged version of the 1991 American Journal of Physics article by Billah and Scanlan,¹ but it is clear to me that the content of that article has not permeated the physics community.