Shape and trajectory of a tumbling elastic sheet of paper II

We investigate the dynamical coupling between the tumbling motion and elastic deformation of a paper strip freely falling in air. Recent experiments suggest the existence of a critical length above which the strip bends as it tumbles. We demonstrate that this bending is caused by the centripetal force associated with its tumbling motion. A simple theory predicts that bending occurs above a critical length in much the same way that buckling occurs in a compressed beam. We further discuss the influence of bending on the trajectory of paper strips, as well as biological implications for the dispersal of seed pods.