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.