Generally, collisions can be described as either elastic or inelastic. And it's going to be important to figure out which kind you're dealing with, because the math works in very different ways.

Physicists recognize two distinct types of collisions: “elastic” and “inelastic.” They have technical definitions, but we won’t go too far wrong if we think of an elastic collision as ...

"Searching for elastic collisions is still the main thrust of SuperCDMS, but considering inelastic collisions opened an avenue to dark matter parameter space that the experiment was not previously ...

Cite this: Inelastic Compression Legging Produces Gradient Compression and Significantly Higher Skin Surface Pressures Compared with an Elastic Compression Stocking - Medscape - Jan 01, 2008.