Unanswered question have answers in physics.se .
Is it a bug or unaccepted answers also show up in this section?
From Why does the “Unanswered Questions” tab show questions that have answers? at Meta Stack Exchange,
Unanswered Questionstab shows questions that have no answers with a positive score nor an accepted answer. (That includes questions with no answers at all.)
This is intentional, and it reflects the fact that just because someone has added content through the
answer field it doesn't mean that the question has actually been answered. The Unanswered Questions tab is meant to get you to questions that have not been sufficiently addressed, and the criterion as posed does as good a job as any number-crunching machine algorithm to do that.
For further reading, see OK, Now Define “Answered" on the Stack Overflow blog, back from 2008.