Throwing of slender elastic projectiles.

Abstract

This study investigates the throw of slender elastic projectiles. By integrating experimental data, numerical simulations, and theoretical analyses, we explore the acceleration and ejection dynamics of these projectiles. We considered various conditions, including the amplitude and frequency of the thrower, as well as the geometrical and mechanical properties of the projectile and its mass distribution. Conversely to homogeneous projectiles, weighted projectiles with a mass at the leading edge exhibit strong lateral deformations that substantially influence their dynamics. This results in an increase in kinetic energy compared to rigid objects. This superpropulsion effect is maximum at a particular value of a dimensionless factor, namely, the ratio between the Euler's critical load of the beam and the acceleration force imposed by the thrower. For heavily weighted projectiles with a mass ratio of 2 between the leading and trailing edges, this maximum corresponds to a 160% increase of kinetic energy. Our results contribute to a deeper understanding of the mechanical behaviors influencing elastic energy transfer in slender structures, with potential applications in sports and robotics.