"누구의 머리카락은 짧아요?"
Translation:Whose hair is short?
I see what you're saying though actually in English "whose hair is short?" could also be used for the first scenario you described. E.g. "We need someone with short hair, whose hair is short?". Both who and whose in English can be used to clarify the subject as well as to ask around and find out for who (among the rest) something is true. You might for example hear "who has a charger?" in place of "does anyone have a charger?"