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 ...

Elastic and inelastic collisions are just the two extreme ends of the collision spectrum. Most fall somewhere in between, in that the objects don't stick together but kinetic energy is not conserved.

Students learn to define, give the MKS units for, and calculate momentum.