How do I stop physical abuse?

My mother physically abuses all of the kids (Including me) to reinforce discipline. Most of the time it really goes to far. For example: My brother refused to eat some corn my mother had set out on the table. He claimed that his tooth hurt. He continuously tries to eat the corn after being forced by mother but starts to cry. She starts whacking him, in the face and on the arms and says "Eat the f*cking corn!". My brother continues to cry and give eating the corn a shot. My mother continues to hit him because he can't eat the corn. My sister stands up in his defense, telling my mother not to hit him (by the way my brother is only 6 years old) and she gets up and slaps my sister across the face. Then, I stood up and told my mom to stop it. After continuously telling my mom to stop hitting my brother, she tells me to shut up, and that when she gets to me she will slap me. When the madness was over I went on the computer to do some homework. My mom follows me to the computer room and starts slapping me for "rooting" my brother. All I can think is "WHAT THE HELL?!" then I say something that kind of crosses the line. Out of the anger and vexation built inside of me I say "I don't give a SH!T!" My mom grabs me by the hair, tackles me to the floor, and starts yanking my head back and forth (using my hair). She puts her legs on my arms and starts whacking me everywhere, across the arms, back, legs etc. This has been happening ever since I was a small child. The exact same type of thing. First of all, this is considered physical abuse, right? Not the disciplinary type of ? I don't want to call the police, but how do I stop this? My dad knows but he is at work all week, and sometimes he says that "I wasn't listening or I shouldn't talk back.". Whenever I tell my mom its illegal she says "Oh, so you know your rights, so what are mine?" HOW DO I STOP THIS?