In most real physics systems, you have to solve systems of simultaneous constraints in order to get the right answer, i.e. all the guys involved in an interaction are sort of going at the same time. (Though also these systems do tend to have ways to break constraints and subdivide the problem when it gets too big, which then does give preferential movement, but not in a way that any kind of functional programming would solve, because it is inherent in reducing the complexity of the math problem.)

There may be exceptions to this; it is not a subject I keep current with.