This question occurred to me in the context of a previous question of mine, which concerned the etymology of 'physics'.
τὰ φυσικά is 'the collective title of Aristotle's physical treatises' (OED). Here the adjective φυσικά is, as far as I understand, an inflected form of φυσικός, which is derived from the noun φύσις. See the following entries in A Greek-English Lexicon by Liddell and Scott: φύσις and φυ^σικός .
How were these three (τὰ φυσικά, φυσικός, and φύσις) pronounced in classical (4th-century BC) Greek? In particular, how were υ and ὺ pronounced? Was it like the IPA /y/ (close front rounded vowel) or like the IPA ⟨u⟩ (close back rounded vowel), or something else? How were these words accented?