Ideally, they should go to chat.
Since chat requires 20 rep, then I think that they should be allowed. math.SE seems to be fine with them (judging by a question about the various dels I asked there).
We shouldn't waste too much time answering them (hypocrisy on my part; I did a bit of Googling to get some details on the question you mentioned). If you know the answer, answer it. If you don't, don't research it yourself.
After all, physics.SE is, among other things, a way to connect with people in sync with the physics world. If you don't have a friendly neighborhood physicist, this place is great for finding answers to little stuff that only these people know. I doubt anyone I know would have known that distance comes from strecke.