As a fellow software developer, if someone puts the qualification "physics programmer" on their resume I would expect them to know the fundamental aspects of physics simulation.
Using a library is an entirely separate thing, as you can use the library without understanding the fundamental concepts of the library. It's entirely possible for someone to use Ogre3D (a popular graphics library) to render out a simple scene for a project, but to say that they know the workings of Ogre3D would probably be a stretch at that point.
IMO for a resume, it's only worth putting down the technologies that you actually understand quite well. Alternatively if it was for a specific company, or a project within the company, I might list it under my experience with that company.
The best place for this sort of thing, especially when it comes down to personal or hobby work, would be the Cover Letter. Here is an except from a cover letter that actually got me a job:
I have been working independently on a video game project over the past 2 years in C++. I have utilized Ogre3D for my graphics, and I implemented in physics via Bullet with a custom wrapper, as well as audio via the open-source stb_vorbis. I have prepared several demonstrations of my work as a hobbyist programmer, and you can view my portfolio at -redacted-.