Mentally torched my mother

my mother is getting mentally torched by my father.as he is telling slang languages and some time he tries to beat my mother.he is a government employee under police. he is trying to say that my mother have not any independent in her house what my father says it will be done by us.why ????my mother is wife of his .so why cant she get independent in her house. my father doesn't likes to get my mother to her parents house .as my mother have not their mother and father so where my mother will go. some times tell me to get out from my house .i am only 18.so what can i do at this situation. last day also he stopped talking with my mother .and i decided that if he does like this i will complain against him to a local police station. when my grand mother was ill (means my mothers mother) she was in my house . my father also torched mentally and next day she was ill by a brain pain .when my mother tells to take him to a doctor he told that it is a drama after that my grand mother gone dead by brain stoke .so how many years did my mother stooped like this please give me some suggestion that what i can do