如图所示，PQS是固定于竖直平面内的光滑的
圆周轨道，圆心O在S的正上方，在O和P两点各有一质量为m的小物块a和b，从同一时刻开始，a自由下落，b沿圆弧下滑。以下说法正确的是
A．a比b先到达S，它们在S点的动量不相等
B．a与b同时到达S，它们在S点的动量不相等
C．a比b先到达S，它们在S点的动量相等
D．b比a先到达S，它们在S点的动量不相等
答案：A
| 完形填空。 A terrible earthquake happened in Wenchuan on May 12, 2008. 1 people lost their lives and homes. During those days, a lot of stories about 2 could be heard. Here is one of them. After the earthquake, 3 a fallen building, some soldiers found that a 4 died in a very strange way. When they were ready to take her away, they were surprised to find that a baby in her arms was 5 alive. The baby was sleeping and 6 hurt at all. Between the dead mother _ 7 the living baby, there was a mobile phone with a short 8 on the screen, "My dear baby, if you can survive , remember that I love you." Everyboy 9 when they read these words. Besides this story, many other stories also moved us deeply. 10 these stories, we know more about love. You're lucky if you're loved by others. You're great if you love others when you're in danger. | ||||
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