How can one deal with arrogant professors?

im a student of a reputed arts and science college . our professors are generally open minded and friendly though most of them doesnt teach anythin worth. but got tis one lady prof from last year who s arrogant and partial compared to others. during exams she comes 15 mins earlier than the said time and give the questions. then she ask us to stop writing wen ever she feels like. wen we say tat the said time is not over her reply is "anyway you ll get 60%".. she was a rank holder durin her acdemic carrier in the same colg and in the same department . but still she behaves like an idiot.most of my classmates also hav the same opinion except her favourites ie, some north eastern girls.wat makes me irritated is tat none of us reacts as we fear abt internal marks. can anyone suggest a way to deal wit her??????