Ok so I have a friend who will sometimes act weird around her house. She always wants to leave the house and hang out far away from there. I know shes cool with her mom, so I know its the dad shes wanting to be away from. Now if I found out he was hitting her, what would happen to him if I told the police? I think he could be hitting her mother/his wife. What would happen if he was just hitting the mother?

Im not going to do anything until I find out for sure whats going on. I just hope my friend would tell me. For all I know she may want to protect her parents, mostly the father I guess.

So yeah, I just want to know what would happen to the father. Thanks.

The concern should not be what happens to the Dad if he is in anyway hurting/ abusing a member of the family.
IF you have any reason to believe he is hurting someone, you should call Child Protective Services and them investigate the matter.

But your question was what could happen....they might arrest him, remove him from the home, order him to get counseling. or do nothing at all... it is hard to say what will happen without all the facts.