问题
多项选择题
如图所示，轻质弹簧下挂重为300N的物体A，伸长了3cm，再挂上重为200N的物体B时又伸长了2cm，弹簧均在弹性限度内若将连接A、B两物体的细绳烧断，使A在竖直面内做简谐运动，下列说法中正确的是（）
A.最大回复力为300N
B.最大回复力为200N
C.振幅为2cm
D.振幅为5cm
答案
参考答案：B, C
搜题请搜索小程序“爱下问搜题”
如图所示，轻质弹簧下挂重为300N的物体A，伸长了3cm，再挂上重为200N的物体B时又伸长了2cm，弹簧均在弹性限度内若将连接A、B两物体的细绳烧断，使A在竖直面内做简谐运动，下列说法中正确的是（）
A.最大回复力为300N
B.最大回复力为200N
C.振幅为2cm
D.振幅为5cm
参考答案：B, C
根据下列材料回答以下回题。
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哪一年C省房地产开发投资增长额最多( )
A．2006年
B．2007年
C．2008年
D．2009年
完形填空(本题共15小题, 每小题1分, 共15分) On my first day of high school, I met David. It was cloudy. When I went home after school, I saw a boy also walking back home. He was my classmate, David. He was carrying his books. 21._______ he was walking, I saw a group of kids rushing to him. David 22._______ and his glasses went flying. All his 23._______ fell on the ground. Then the kids ran away. He looked up and I saw sadness in his eyes. I helped him stand up and 24._______ his glasses. Then I saw there 25._______ a big smile on his face. From then on, we became 26._______. The more I got to know David, the more I liked him. During the four years, we always studied, played together and had a 27._______ time. On the day when we finished high school, I could see that he was 28._______ about his speech. So I said, “Don’t be stressed out. Believe in 29._______ and you’ll be the best!” Then he began, “Today is a good time to say 30._______ to those people who helped you succeed through the difficult years. Our parents, our teachers, but mostly our 31._______. Being a friend to someone is the best gift you can give them. I’ll 32._______ you a story…” I just looked at the handsome popular boy amazingly when he told the story of the 33._______ day when we met each other. All of us were 34._______. Everyone was listening to his story in silence. I saw his parents looking at me and smiling. I did not know the deep meaning 35._______ that moment. I know even a small action can change a person’s life. As you know, “Friends are angels to make us rise when our wings have problems flying.”
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