问题
单项选择题
采用滑轮组来吊重物时是为了减小吊钩承重，每增加一个动滑轮，其所受的力应为（）。（不考虑拉绳角度）
A.总重量/拉绳量
B.1/3总重量
C.一半的总重量
答案
参考答案：A
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采用滑轮组来吊重物时是为了减小吊钩承重，每增加一个动滑轮，其所受的力应为（）。（不考虑拉绳角度）
A.总重量/拉绳量
B.1/3总重量
C.一半的总重量
参考答案：A
| 用方框中所给词和短语的适当形式填空，使短文意思完整。每个只能用一次。 | |
Not too long ago, I was 1_____. I told my mother all about it, hoping for some pity. Instead, she said, "I heard Jamie was having a difficult day too. 2_____ don't you make her some cookies?" I didn't 3_____ want to do that, but I didn't want to go back to my other problems, either. I made the cookies and 4_____ them in a box. Then I made a card with some 5_____ on it and wrote a small note. That afternoon I went to my friend's 6_____. When Jamie came to the door, she looked at me 7_____. Before she could say anything, I said, "I heard you were having a hard day and decided to bring you 8_____. I hope your day goes better. " The look on Jamie's face was one that I could never put into words. It was 9_____ a dark sky suddenly, turned into sunshine. When I 10_____, I felt a lot better. That day I knew that those who brought sun-shine to others, could also keel), it for themselves. |