质量为2m的A球和质量为m的B球放置在光滑水平面上，中间有一弹簧（未拴接），弹簧处于压缩状态，现将A、B同时由静止释放，发现A球刚好到达高为H的光滑斜面顶端，B球顺利通过半径为R的光滑圆形轨道的顶点且对轨道顶点的压力大小为mg．其中，H、R未知．求：

小青同学乘火车从沈阳（东北平原）出发到乌鲁木齐（天山脚下）去旅游，他在旅途中能见到的自然景观依次是（    ）

完形填空。

    Hello, I am John. Look, this is a picture 1my room. I have a nice bed in the middle of my room. There is a big table 2 the closet and the bed. Many clothes are 3 the closet. A white air-conditioner is4 the wall beside the window. There is a computer on the table. I often write e-mails with it.

    Do you like my room? What's your room 5? Can you tell me, please?