If the last syllable is long (but unstressed of course) an acute stress is placed on the syllable before, on the penult. Even if the word was stressed on the antepenult in the nominative, such as ὁ ἄνθρωπος. Or if it had a circumflex on the penult in the nominative, like ὁ δοῦλος for instance. Why? Because that is the easiest way to pronounce those words.
Says who? Said the Greeks!
Try this: ἄνθρωπος. That's fluent and easy.
Now try ἄνθρωπου with a long UNstressed ου at the end.
It's easy to say ἄνθρωποῦ (2 stresses). But: a word can only have ONE stressed syllable (in normal, everyday speech, even in ancient Greek).
||All right you say. So what about "ἄνθρωπός ἐστιν"? That's got 2 stresses. Yes, but "ἐστιν" doesn't have any, leaning as it does on "man" (see enclitics). So "man" or any other antepenult needs strength and accents for 2.|
Now try this: δοῦλος , really long οῦ , short ος . No problem.
Examples Remember that plural -oi and -ai are short!
So now try: δοῦλῳ dragging out both syllables but stressing only the first. Same as above for ἀνθρώπου, δοῦλῷ (two equal long stresses) would be easy but would make for funny, stilted speech. δούλῳ sounds much better.
Examples And here the recording of the following examples:
ὁ τοῦ Φιλίππου πατήρ
τὸν Φίλιππον καλεῖ
τῷ Φιλίππῳ λέγει
ὁ τῶν δούλων βίος
τοῖς δούλοις λέγει · ὦ δοῦλοι, ...
τοὺς δούλους καλεῖ
τὸν δοῦλον βλέπει
ἐν ταῖς Ἀθήναις
Enough of this. It's up to you now. Read all your Greek out loud till it sounds right.