Physics is about stories grounded in evidence, reliable enough to act on. About what
will-be and what
may-be: about prediction and possibility(and so also about what
may-not-be, or impossibility).
To make quantitative predictions rely on relationships between quantities: these relationships are either
constraint, or a combination of these two kinds.
To figure out what could happen, find frozen moments (maybes in a possibility space). This is reasoning with constraints.
Of all the things you could imagine happening, only some are actually possible, and these depend on what’s the case now. (You’re picking out possibilities in phase space.)
Conservation laws are examples of constraints. Mass is conserved; momentum is conserved; energy is conserved. There is a common pattern of reasoning across these three that could be fruitful.
Thinking within the box
To figure out what will happen, reason with accumulations.