inelastically

Inelastically is an adverb describing processes that do not preserve kinetic energy in macroscopic interactions or that involve internal energy changes, permanent deformation, or dissipation of energy as heat or sound. The term is most often used in physics, engineering, and materials science to distinguish non-elastic behavior from idealized elastic responses where kinetic energy is conserved.

In the context of collisions, inelastic means that some of the system’s initial kinetic energy is transformed into other forms, such as internal energy, deformation, or radiation. The degree of inelasticity is commonly quantified by the coefficient of restitution, a value between zero and one. A perfectly inelastic collision, where the objects stick together, is the limiting case where the post-collision kinetic energy is minimized.

In materials science and solid mechanics, inelastic deformation occurs when a material yields or accumulates permanent strain under stress. This includes plastic deformation, where shape changes persist after unloading, as well as viscoelastic behavior, where energy is dissipated over time due to internal friction and time-dependent rearrangements of the material’s structure. Inelastic responses are contrasted with elastic responses, in which deformations vanish when the applied load is removed and energy is largely recovered.

Inelastic processes also appear in other domains, such as inelastic scattering in particle and nuclear physics, where incident particles lose energy to a target, producing excitations or new particles. In geophysics, anelasticity describes time-dependent attenuation of seismic waves due to internal friction within the Earth. Overall, inelastically describes phenomena where energy is not fully conserved as kinetic energy during interaction.