What are fixed-target collisions?

Fixed-target collisions are like when one toy crashes into another that’s just sitting there, waiting to be hit.

Imagine you're playing with marbles. You roll a marble, let's call it Marble A, toward another marble, we'll name it Marble B, that’s already on the floor. Marble B doesn’t move until Marble A hits it. That’s a fixed-target collision: one object moves and crashes into another that stays put.

In this kind of crash, Marble B is the fixed target. It doesn't run or jump, it just waits for the hit. This makes it easier to see what happens next: Marble A might stop, or it might knock Marble B away, or even both marbles could roll off in different directions.

Think about it like this: if you’re on a skateboard and you crash into a tree that won’t move, that’s also a fixed-target collision. The tree is the fixed target, just like Marble B. You're the one doing all the moving, just like Marble A.