If the question is about physics, then the content of that question does not determine if it is on topic or off topic. "Is is possible" physics questions can be on topic or off topic depending on what the goal is.
If the question is asking in order to further a personal theory or design a product (engineering), then I would say it is not for PSE.
If the question is asking if something is possible in the context of trying to better understand a specific physics concept, then I would say it is on topic for PSE.$^*$
$^*$ Of course, the question also needs to follow other site policies, be understandable, be focused, etc.