An old New Scientist folk-tale:
Imagine, an ideal, perfectly rigid and symmetrical impact: no elasticity, no time or space-warp, no escape-bullshit:
A speeding train goes one way, and a speeding bullet rushes to clash it's front.
At the moment of impact the bullet which naturally bounces off the train's front, reverses it's direction.
When reversing it's direction there is a very short moment in which it is stationary, at "zero" speed.
This short resting moment it when it touches the train.
Did the bullet manage to stop the train, even if for the briefest of moments?