题目

如图所示，滑块A、B的质量均为m,A套在固定倾斜直杆上，倾斜杆与水平面成45°,B套在固定水平的直杆上，两杆分离不接触，两直杆间的距离忽略不计且足够长，A、B通过铰链用长度为L的刚性轻杆(初始时轻杆与平面成30°)连接，A、B从静止释放，B开始沿水平面向右运动，不计一切摩擦，滑块A、B视为质点，在运动的过程中，下列说法中正确的是A. 滑块A在运动过程机械能守恒B. B滑块最大速度为C. 当A到达与B同一水平面时,A的速度为D. B滑块到达最右端时,A的My best friends gave me a present in a box on my birthday. It was a little heavy, which made me very curiously. So I intended to open it at once but she prevented me do so. She said I mustn’t open it until I went back home but gave me a naughty smile. Although there is a strong desire in my mind to know that was inside the box, I just did as she said. On the way to home, all I did was thinking about the puzzle. Finally I opened the box. It was a cup printing with a pink word — friendship. It was so lovely that I liked very much.Now, every time I use a cup, I will think about her and the friendship between us.