Confusion and Illusions in Collision Theory (original) (raw)

2023, ForsChem Research Reports

Material collisions (and interaction processes in general) play an important role in most, if not all, physicochemical phenomena observed in Nature including (but not limited to): Chemical reactions, diffusion, viscosity, adhesion, pressure, transmission of forces, sound, and momentum and heat transfer, just to mention a few. It is quite surprising that a unique, clear, objective definition of "collision" is missing in most scientific textbooks and encyclopedias. In this report, some missing definitions in collision theory are proposed aiming at providing a more clear language, and at avoiding the confusion emerging from the lack of objective definitions. In addition, the illusion of elasticity of collisions is discussed. While elastic collisions are clearly defined as collisions with no change in the macroscopic translational kinetic energy of the bodies, the subjective definition of the bodies, and the inevitable simultaneous occurrence of multiple additional collisions involving internal components and/or external bodies may lead to different conclusions about the elastic character of a collision. Interaction processes involving composite bodies (having multiple components and an internal structure, like all bodies known to us so far) are typically inelastic or superelastic, but the overall result of many consecutive interactions, may resemble an elastic behavior. True perfectly elastic interactions can only be observed between isolated pairs of rigid, indivisible, structureless bodies, like the hypothetical "true atoms" proposed by the ancient Greeks.