# How does a (near) elastic collision work at a microscopic level?

Suppose a large mass $M$ travelling at $v$ impacts a small stationary mass $m$, then following through the elastic collisions from high school, we get that the smaller mass can exit the collision FASTER than $v$.

In the limit of huge $M$, we can change reference frame and make $M$ basically stationary, and $m$ simply bounces off, thereby having a velocity change of $2v$.

How can I visualise this from a microscopic level? If the normal force between objects only exists while they are in contact, the moment contact was lost between two objects they no longer act on each other. So as soon as the target balls speed reaches the tiniest amount above the impact ball speed, the balls should separate and no longer interact. This would lead to all collisions being "sticky" and completely inelastic.

So why are not all collisions sticky? How do collisions work that apparently allow acceleration past the point where contact is lost? And if this is something to do with Coulomb interaction, is there any historical commentary on how Newton and peers felt about this prior to the understanding of electrodynamics?