The preposition. If it were the separable verb, in this sentence it would all be together at the end. With separable verbs, either the prefix goes to the end (leaving the main body of the verb towards the start), or it all goes to the end. The prefix never stays at the start with the rest at the end, so in a scenario such as this you can eliminate the possibility that it is the separable verb.
no it is not, when asking sb about sth (i.e. making an inquiry) 'jemanden nach etwas fragen' is the correct stock phrase. now when trying to let sb know that you are asking them a question then you can use 'jemanden etwas fragen' - which can mean to ask sth/to ask a question. see this link : https://www.gutefrage.net/frage/wo-liegt-der-unterschied-zwischen-etwas-fragen-nach-etwas-fragen-und-wegen-etwas-fragen
p.s. if you are trying to ask for advice or permission then 'jemanden um Rat/Erlaubnis fragen' is the stock phrase.
hope this helps.
OK, so can you substitute a person in place of "Gewicht" and have this sentence mean that you are inquiring after someone? E.g. "May I ask after your mother?" "Darf ich nach ihrer Mutter fragen?" Or would that just mean you were asking who your mother is? Am confused between the literal translation and how the sentence would be understood. Help?
"Nach etwas/jemandem fragen" is pretty much equivalent to "ask about something/someone" in English. (Which I guess is about the same as "ask after." I'm not really familiar with "ask after"; I think it's kind of old-fashioned.) So you could be asking anything about the mother-- who she is, where she is, what her job is, or whatever.
(By the way, you should have capital "Ihrer" for that sentence; otherwise it means "her" or "their.")
As someone from England, I'd say it was actually slightly better as long as it was structured:
May I ask, 'what is your weight'?
I've never heard anyone say "May I ask your weight." I don't think I've ever asked this question myself, but if I had to then I'd probably say "May I ask how much you weigh?"