Investigating chirping steel balls: a novel set-up

摘要

The International Young Physicists' Tournament (IYPT) is a worldwide, annual competition for high school students. This paper is adapted from the author's investigation into problem 4,Ball Sound, of the 27th IYPT. A novel set-up is proposed to investigate the unusual 'chirping' sound produced when two hard steel balls, or similar, are brought gently into contact with each other. It is shown that the decreasing time interval between rapid successive ball collisions, and not surface acceleration, is responsible for the chirping phenomenon. The proposed set-up simulates the collision of steel balls using our hands, and provides effective physical insights into the mechanism of chirp production.