Intuitive understanding of the relationship between the elasticity of objects and kinematic patterns of collisions

Horizontal collisions have long been used as a tool for exploring people's intuitive understanding of elementary physical laws. Here, we explored intuitive understanding of the relationship between the kinematic patterns of collisions and the elasticity of the colliding objects. In Experiment 1A, we manipulated the simulated materials of two virtually colliding spheres and asked the participants to judge whether the simulated collisions appeared "natural" or "unnatural." We did the same in Experiments 1B and 2, but asked the participants to adjust the velocities until the collisions appeared to be "perfectly natural." In Experiment 3, we removed pictorial cues to the materials of the colliding spheres and asked the participants to rate the bounciness of the materials, in view of the kinematics of simulated collisions. Overall, the results showed that observers intuitively understood that collisions between more elastic objects subtend a higher coefficient of restitution than collisions between objects with lesser elasticity. The results also highlighted some discrepancies between the intuitive and Newtonian physics of collisions. Observers were somewhat insensitive to violations of the principle of energy conservation, and their responses were influenced by irrelevant kinematic features of the collisions, such as the collision type and precollision velocity. We discuss our experimental results in relation to salient theoretical perspectives on intuitive physics.