问题 选择题

A、B是两个几何形状完全相同的带电金属小球,且qA=qB=Q,在真空中相距r,它们相互作用的斥力为F,引入第三个形状完全相同的金属球C,球C不带电。现将A、B两球同时与C球相接触后,移到原来相距r的位置,则A、B的作用力是(    )

A、     B、      C、    D、

答案

答案:A

题目分析:接触前,AB的作用力为,

当三者同时接触后:根据平均分配原则,最后AB小球都带,故作用力变为:

故选A,

点评:做此类型题目需要清楚平均分配原则,以及公式中的变量和不变量

阅读理解

阅读理解

                                             Come And Join Us!

      We warmly welcome you to the Shine Sports Centre!

      All the young people in this city can become members of the Shine Sports Centre and each member

should pay $10 every year. To be a member of us and get your membership card(会员卡),you need to

come to us between 2 pm and 6 pm, Monday to Thursday. I have to tell you that we don't accept new

members on Friday. Now, there are three things that you must remember to bring with you when you

come for a membership card. They are your ID card, a recent passport-sized photo of yourself and the

money. We can't give you the card unless you bring all three.

      Once you have got your membership card, you need to bring with you whenever you come to book

or use any Shine Sports Centre facilities(设备).Booking over the phone is not allowed, so you have to

come here with your card when you want to book. There is one more thing I have to tell you. Our opening hours is from 9 am to 10 pm on weekdays and from 10 am to 6 pm on weekends. We hope that every

member can have a great time in the Shine Sports Centre.

1. You can use the facilities in the Shine Sports Centre at_______.        

A. 9 am on Sunday                

B. 5 pm on Wednesday  

C. 7 am on Thursday              

D. 9 am on Saturday

2. You and your classmate have to spend ______.on the membership card for two years.

A. $10          

B. $20              

C. $30              

D. $40

3. What does the underlined word "book" mean in Chinese in this passage?  

A. 书            

B. 账册            

C. 预定            

D. 记录

4. Which of the following is TRUE?

A. All people have the chance to be members of the Centre.

B. You can get the membership card at 6 o'clock in the morning.

C. You can't book the facilities over the telephone.

D. You don't need to bring the membership card when you need to use the facilities.

5. Who is the advertisement written for?

A. Young people.  

B. Old people.        

C. Couples.      

D. Little kids.

单项选择题