If you are prepared to do something, you are willing to do it if necessary. 愿意的
adjective [原级]有准备的,准备好的;打算做,乐意做;提前准备好的
If you are prepared for something that you think is going to happen, you are ready for it. 作好准备的Police are prepared for large numbers of demonstrators. 警察对大批示威者有准备。