This is an ongoing point of discussion/contention/etc. over at Physics SE. We have an off-topic close reason which reads as follows:
Homework-like questions should ask about a specific physics concept and show some effort to work through the problem. We want our questions to be useful to the broader community, and to future users. See our meta site for more guidance on how to edit your question to make it better.
Here is the meta post to which the close reason refers: How do I ask homework questions on Physics Stack Exchange?How do I ask homework questions on Physics Stack Exchange?
This close reason gets a lot of use and really helps keep down the junk level. However, the close reason does have some problems. In a nutshell, it's not really clear what "homework" means. I can post a question which came up in the context of research but which is in all ways qualitatively like a homework question (i.e. I just want to know the numeric answer and I'm not asking anything conceptually interesting). As pointed out by others here already, whether or not a question is homework isn't the issue so much as whether or not it's just asking for the answer to a problem without any interesting conceptual core or lacks research effort.
We recently considered renaming the "homework policy" to reflect this. Here are two relevant meta posts:
Should we rename the homework policy?Should we rename the homework policy?
Generalizing the homework policyGeneralizing the homework policy
I'll be following this meta post as a source of inspiration for our own improvements in the physics site.