Questions & Answers about Я спрошу учителя завтра утром.
Why does спрошу mean "will ask" when the -у ending usually means present tense?
You are right that -у is the "I" ending for the present tense. However, спрошу is a perfective verb, meaning it describes a one-time, completed action. Because a completed action cannot happen right now in the present, adding present-tense endings to a perfective verb automatically creates the simple future tense: "I will ask".
Could I use the future word буду and say я буду спрашивать instead?
You could, but it changes the meaning slightly. Спрашивать is an imperfective verb (focusing on the process). Using буду with it means "I will be asking" or "I will ask repeatedly". Using the perfective verb спрошу shows you will ask the question once and the action will be completely finished.
Why does the word for teacher change from учитель to учителя?
The teacher is the direct object here (the person being asked), so the word must be in the Accusative case. For masculine nouns that represent living things (animate nouns), the Accusative case borrows its ending from the Genitive case. The soft sign at the end of учитель changes to -я, making it учителя.
If завтра means "tomorrow", why do we change утро to утром?