题干

如图所示,三角体由两种材料拼接而成,BC界面平行底面DE,两侧面与水平面夹角分别为30°和60°。已知物块从A静止下滑,加速至B匀速至D;若该物块静止从A沿另一侧面下滑,则有(  )

A:通过C点的速率等于通过B点的速率

B:AB段的运动时间大于AC段的运动时间

C:将加速至C匀速至E

D:一直加速运动到E,但AC段的加速度比CE段小

上一题 下一题 0.0难度 选择题 更新时间:2019-08-21 04:10:14

答案(点此获取答案解析)

B

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    "Homestay is a form of study abroad program. It allows the visitor to rent a room from a local family to better understand the local lifestyle. It also helps to improve the visitor's language ability," said a teacher during a school meeting last term. "Students who wish to learn more about foreign cultures or to get foreign experience should join this kind of holiday. I am sure you won't be disappointed."

    After this special meeting, I always thought about this kind of holiday. Last month, I had a chance at last to go on such a holiday with some of my schoolmates and we went to London, a place where I had wanted to go since years ago.

    As we were still young, we had a group leader who planned things for us and looked after us. After we got to London, we went to stay with different families. I was lucky that my host family was a white couple who had a daughter about my age. They treated me as a daughter of their family during my stay there. They were interested in me and I learned a lot of things from them, too.

    The holiday was filled with activities every day. After breakfast, a local teacher would come to take us in his car. Then we would have classes or go on a sightseeing trip to different places of interest like the Big Ben, the London Bridge, and the Buckingham Palace. We would go back to our own homes after the activities

    The holiday was a valuable experience for me. I enjoyed every minute of it. Yet, time really flew fast. Three weeks later, we had to leave "home" for Hong Kong.