N2
というものだ
Speaker's impression, Criticism or conclusion
何があってもお互い助け合うのが友達というものだ。
Helping each other no matter what is just what friends do.
Explanation
Added to the end of a sentence, it is the speaker's strong judgment based on common sense: 'that is exactly what ... is'. It has two moods: admiration, 「これこそ運命というものだ」 (This is what fate is); and criticism, 「一言の断りもなく他人の物を使うなんて、非常識というものだ」 (Using other people's things without a word is just lacking common sense). It is the speaker's own firm opinion.
Mixed up with
「というものだ」: the speaker's strong personal judgment. 「一人で全部やるのは無理というものだ」 (Doing it all alone is simply too much).
「ということだ」: hearsay ('I hear that ...') or an objective explanation ('that means ...'), with no personal judgment. 「彼は来月結婚するということだ」 (I hear he's getting married next month).
Its negative counterpart is 「というものでもない」 (not necessarily).