Coefficient of Restitution Measurements for Sport Balls: An Investigative Approach

Abstract

Studies of collisions in the introductory laboratory often use carts moving on air tracks or along dynamics tracks. As an alternative, students in our laboratories study collisions through experiments that determine coefficients of restitution ε's of balls used in sport. Since ε's are crucial to the outcome of many sporting events, such activities provide students with a “real-world” context for studying collisions. In the process of investigation and analysis, students learn about inelastic collisions, energy transfer, and elasticity of materials.

Reflections on a Bouncing Ball

“…In particular, the COR of a vast array of sports balls have been studied as a function of impact velocity. [12][13][14][15][16][17] Depending on the circumstances of the experiment (material of ball and impact surface, mass, range of impact velocities and drop heights), COR values have been reported to decrease, 3,4,10,13,[16][17][18][19] increase, 3 and remain the same 4,14,15,17,19,20 with increasing impact velocity.…”

Measuring the coefficient of restitution and more: a simple experiment to promote students’ critical thinking and autonomous work

“…Measuring e for different materials using balls is an usual teaching activity that has been discussed in different works [4][5][6][7][8][9][10][11][12]. The method described here has less exper imental difficulty than required in other methods [4,6,8,13,14], which reduces possible sources of experimental error and also allows students to measure smaller values of e. In addition, the method described here requires less numerical analysis than other previous methods [8], what makes it suitable for students with lower mathematical skills. The main difference between the above mentioned works and the work described in this paper is that here we propose and evaluate simple activities to go beyond the determination of the coefficient of restitution and help students analyse the physical model and the approximations considered in the experiment.…”

Proposta experimental do estudo de colisões entre bolas de borracha e superfície plana

“…Os valores obtidos para o coeficiente de restituição estão próximos aos determinados por [10] para bolas de tênis, futebol, basquete e golfe indicando, portanto, a similaridade de comportamentos das bolas empregadas.…”

“…Do ponto de vista do ensino, além de ser um tópico básico em física, estudar o movimento de queda livre de bolas reaisé motivador e desperta atenção dos alunos devidoà natural associação que se faz com o impacto de bolas usadas em atividades esportivas [10,11]. Este tema, em particular, tem sido estudado por Cross [12] e pode ser abordado e adaptado em nível adequado de compreensão para alunos de cursos introdutórios de física básica.…”