补出下列名篇名句中的空缺部分。

①《论语·泰伯》中论述“士”要抱负远大、刚强勇毅、责任重大的两句是“____，____”。

②李白在《蜀道难》中描写急流和瀑布飞泻、发出巨大声响的诗句是“____，____”。

③杜甫的《茅屋为秋风所破歌》中“____，____”，两句以孩子梦中蹬破被里的描写来表现当时诗人一家生活条件的艰苦。

    We each have a memory（记忆力）. That's why we can still remember things after a long time. Some people have very good memories and they can easily learn many things in a short time, but some people can only remember things when they say or do them again and again. Many of the great men of the world have got surprising memories.

    A good memory is a great help in learning a language. Everybody learns his mother language when he is a small child. He hears the sounds, remembers them and then he learns to speak. Some children are living with their parents in foreign countries. They can learn two languages as easily as one because they hear, remember and speak two languages every day. In school it is not so easy to learn a foreign language because the students have so little time for it, and they are busy with other subjects, too.

    But your memory will become better and better when you do more and more exercises.

如图，有质量分别为m₁、m₂的两个物体通过轻弹簧连接，在力F的作用下一起沿水平方向做匀加速直线运动（m₁在光滑地面上，m₂在空中）．已知力F与水平方向的夹角为θ．则m₁的加速度大小为（   ）