Waking up is not the same as getting up, neither in English nor (as far as I know) in Russian (I believe: wake up = просыпа́ться). It's perfectly possible to be awake already but not getting out of bed yet. I would agree that "I need to get up at five" and "I need to wake up at five" convey pretty much the same meaning (and misery ;-) ) but strictly speaking there's a difference.
it is за + Accusative. E.g., за два часа, за неделю, за день, за пару лет.
You can also use занять (занимать). It is used to express how something "takes" a certain amount of time:
- Проверка конструкции заняла два дня. = Checking the structure/construction took two days.
Thanks for the reply. :-) But I'm surprised, because the distinction I read was with regards to "when to use one versus the other". So although I'm sure you've covered this many times, is there then a "general rule" for when to use one vs. the other that you can recommend?
Нужно matches its subject in gender/number (ну́жен / нужна́ / ну́жно/ нужны́):
- Нам нужна вода.
- Актёр больше не нужен.
- Очень нужно молоко.
- Нам нужны булочки.
Надо has no forms and cannot do that, so it is much more limited in its use with nouns. You can occasionally encounter sentences like "Здесь надо стол" or "Нам надо коробку" but these are not standard (and may depend on the region—people do not speak that way where I live).
However, structures like "Не надо паники", "Надо больше денег" or "Надо воды" are widely used (note how the noun does not directly function as a subject here).