Is it proper to say this:
"Everything happens for a reason, and that reason is usually Physics."
I would not say that. Purely semantically, the sentence is too vague. Physics is an area of study, a specific method of research about one specific aspect of the known universe. It is not a reason, and therefore it is not a reason for anything.
Physics gives you a way to study the goings on of the world. And in turn, gives you predictive power about how an event is likely to proceed. However, it doesn't really give you an (ultimate) reason, since ultimately, physics itself must be based on empirical evidence. A more precise statement might be: "Things happen, apparently according to a set of rules. Physics is the study of such rules."
To take it further.. I think, and I believe this is the standard in science/physics, that "reasons" do not exist fundamentally. If you want a reason you are either appealing to a more fundamental science or a broader philosophy/personal opinion. Since physics is usually the most fundamental science (in the sense that we presume other sciences are or could be derived from it) its nonsensical to ask for a scientific reason for the most fundamental science. The fundamentals are the reasons.
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