I was reading something and one of the character asks another character 「大丈夫？怪我がないか？」. The first sentence obviously means "Are you alright?" but should I parse the second sentence as "You're not hurt, are you?" or "Are you hurt?" In English, when we include a negative in a question, it often implies some preconception that we seek confirmation of, but is that true of Japanese as well? If I wanted to ask, "Don't you know what this is?" (which implies that I expect my listener to know what that thing is), would I say something like 「これは何かわかっていない？」, and would that be different from 「これは何かわかっている？」
A question asked in a negative form translates to a similar negative form in English, but the emphasis is slightly different, in that there is no "unspoken positive assumption"
In other words, 怪我がないか？ Is not "You're not hurt, are you? it's more accurately: "You aren't hurt?"
これは何かわかっていない？ is not something like "You don't happen to know what this is, do you? It's more like "Don't you know what this is?" (but without the implication that not knowing is stupid, the way that question comes across in English)
There is a difference in how these negative questions should be answered, though, because in Japanese, the questioner asking a negative is expecting you to confirm their negative form, or deny it.
In other words, if you answer "yes" to these forms of questions, you are telling them "Yes, (as you said) I am NOT hurt." and "Yes, (you're right) I don't know what that is."
If you answer "no" to these negative forms, you are intentionally creating a negation of their negative question: "No, I actually am hurt!" (although this is an odd way to answer that negative question) and "No, I know what that is, it's ...."
So to go back to your your example, if you ask これは何かわかっていない？ The implication is that you expect that maybe the person actually does NOT know what this is, in a non-judgemental way. And これは何か分かっている？ is not implying an expectation either way.