In the trailer for the latest Terminator film at https://www.youtube.com/watch?v=ui81ZjE-oQQ, at 0:59 Sarah Connor says "если хочешь жить" to a character she's never met before, then at 1:04 when she says his name he replies "ты знаешь кто я?" She then says "Мы ждем тебя..." I'd have thought "если хотите жить," "Вы знаете кто я," and "Мы ждем Вас" would be more appropriate on a first meeting between adults. Can someone explain why ты would be okay?
In a firefight, respecting formalities such as "Вы" would connotate a degree of "hyperfomality" that would be either humorous or imply that the speaker is socially awkward nerdy or overly polite individual. Generally russian language drops into "terse mode" when in combat. The more dangerous the terser it gets.
Also, tho its not the case here, using "Ты" in translated american-set movies is homage to english language lack of ты/вы distinction. It falls on the translator to exercise creative license to figure out where ты or вы is more appropriate based on the context.
They are young people, of the same age, and it is totally possible to use "ты" among such people. Especially if the one who starts such an address is a girl. I often get addressed this way by girls I do not know.
Conversely, addressing by вы would likely show she does not want to do anything with the person except purely official duties (that is speaking as an official person on duty, ex officio, like a police officer, rescuer, etc) or that she thinks that he is too old/unattractive.
I think if he was handicapped or his face was not visible (such as being in a bike helmet or in a mask) she would be more likely to use вы.
"Ты" is intrusion in a private space. If people are friends or relatives such intrusion is usually permitted (and "ты" is used), otherwise "вы" is preferred.
Usage of "ты" in "если хочешь жить" implies that there is no time for formalities: concept of "your private space" is now useless, either you die or you allow someone else to tell what you have to do in order to survive.
Basically this is what happens to Bilbo when he joins the Dwarves in their quest: he has to forget about handkerchieves and other necessities of his prior life (including his private space), because now they tread a dangerous road.