问题 多选题
一个弹簧振子在光滑的水平面上作简谐运动,其中有两个时刻弹簧对振子的弹力大小相等,但方向相反,那么这两个时刻弹簧振子的(  )

A.速度一定大小相等,方向相反

B.加速度一定大小相等,方向相反

C.位移一定大小相等,方向相反

D.以上三项都不一定大小相等,方向相反

答案

BC

阅读理解

阅读理解。

      There would be a school party on Friday evening. The girls were talking about what they were going to wear.

        "I'm going to wear a black dress, so everybody will notice(注意) me,” said Emily. "How about you, Linda?"

     "I'm not sure. Maybe jeans(仔裤),an old shirt, and a hat. People will notice me more than you! " Linda said.

     "But what are the boys going to do in the party?” asked Jane. "Do you remember the last school party, last year? They just stood there, and we girls had to dance by ourselves!"

      "I hear that some of the boys learned how to dance this summer. Maybe it'll be better this time,” said Mary.

     The party was held on Friday evening, groups of students arrived. The music began The girls stood in a line on one side, and the boys on another side. Mr. Green, their teacher, tried to get them together, but

failed. After a while, Tim said, "l don't want to stand here the whole time. The party is only for two hours. It'll be over soon " He started to dance. All the others watched him Then David asked Emily if she wanted

to dance. Then Jack and Linda. Then, all began to dance. Soon there were more dancers than watchers.

1. How long would the party last?

A. On Friday evening

B. For one hour  

C. For two hours  

D. For three hours

2. What kind of clothes was Emily going to wear?

A. A black dress                    

B. Jeans    

C. An old shirt                      

D. Jeans, an old shirt and a hat

3. How did Emily and Linda dance in the school last year?

A. They danced by themselves          

B. They danced with the boys

C.. They didn’t dance                

D. They danced with their teachers

4. How did the boys spend the summer holiday according to the passage?

A They went swimming           

B. They learned to dance  

C. They watched TV             

D. They went climbing

5. Which is not mentioned in this passage?

A There would be a school party on Friday evening.           

B. Their teacher asked them to dance together.  

C. Jack and Linda danced together.             

D. The boys and girls stood together and watched their teacher dance.

单项选择题