My father abuses my family?

He verbally and emotionally abuses my mom, my siblings and I, and he has physically abused my mother. He has spent every last dime my family has and we are currently living off of loans from a friend, but we can't do that forever. I tell my mom every day that she needs to leave him because nobody feels safe living here with him. I go to college next year and I can't wait to leave him, but I am concerned for my little sister and my mom. I'm not sure exactly what my mom is thinking, but it seems as though she is in denial. She'll just tell us (me and my sister), "your father is 100% wrong" and "you don't deserve this", but she doesn't DO anything to stop this. I am sick of putting up with his s h i t (pardon my language) and living in constant terror that he will hurt us. I love sleeping over my best friend's house because I can wake up knowing her family loves each other and they love me, but I feel extremely uncomfortable in my own home. What can I say to my mom to convince her to leave him or kick him out. I don't even know how we would kick him out though since he would just refuse to leave and he has nowhere to go. Please help me, I am so scared.