I'm doing this physics question, which I'll paraphrase:
A car being driven at a constant speed 20 m/s in a straight line goes through a school zone. The car passes a tree, behind which a police car is waiting at rest. After five seconds of passing, the police car accelerates after it, parallel to the path of the other car, at 2 m/s². At the instant when both cars are traveling with the same speed, what are their positions (relative to tree), and why (are they different)?
So I was answering the "why" part of the question, and I thought that the positions of the two cars at that instant in time is different because their respective displacements from the tree are different.
Then I wondered: what caused the displacements to change? It could be the velocity, but I thought that since velocity was derived from a function of displacement over time, it didn't really make sense to me that velocity causes displacement to change, but rather that it was a description of how displacement changes.
More broadly, what causes things to move (with or without nonzero acceleration)?
I've always heard that net Forces cause acceleration, but how does acceleration cause displacement to change?
Edit: I just realized that the same thing can be asked of the relationship between position and displacement.
Edit: Concerning Mauro Giliberti's and Cinaed Simson's comments. If displacement is so connected with velocity that there is a iff relationship, then my question is this: what changes the location of the object as displacement, velocity, etc. is changed?
In the main body of my question, my use of "displacement" involved both the real-life sense (where the cars were and are) and the non-real-life sense (numbers and values). In this edit exclusively, I have gone along with Mauro's and Cinaed's use of "displacement" (if I'm not mistaken) in the purely non-real-life sense. I don't know this whole concept well enough to rephrase "cause" so I hope this edit was adequate.