问题 选择题

如图所示,A、B为两个用绝缘细丝线悬挂起来的质量相同的带电小球,左边放一个带正电的球C时,两悬线都保持竖直方向(两线长度相同),若把C球移走,下面哪个图可以表示A、B两球的位置?  ( A、B没接触)                (     )

答案

答案:B

左边放一带正电的小球时,A B两球保持竖直,说明A B两球受力平衡,根据排除法可知,如果A带正电,B无论带什么电,都满足不了两球保持竖直悬挂,如果A带负电,要想保持竖直悬挂,B必须带正电,所以两球带异种电,两球是吸引关系,故C D错误,由于两球质量相等,所以偏离的幅度应该一样,故A错误B正确。

阅读理解

Most children now chat daily either online or through their mobile phones. They are connecting to a huge number of other children all over the world. Some are shy “in real life” but are confident to communicate with others online; others find support from people of their own age on relationship issues, or problems at home.

Sometimes the online world, just like the real world, can introduce problems, such as bullying or arguments. Going online is great fun, but there are also a few people who use the Internet for offensive(冒犯性的)or illegal aims. Children must be made aware(意识到的) of both the good things and the dangers.

To keep children safe your management must cover the family computer. Just as you decide which TV programs are suitable, you need to do the same for the websites and chat rooms your children visit. Remind your children that online friends are still strangers. Reminding them of the risks will keep them alert(警惕).

Computer studies are part of schoolwork now, so it’s likely that your children may know more than you do. We get left behind when it comes to the latest gadgets(小玩意)and the interactive areas of websites, like chat rooms and message boards, which are especially strange. The language of chat is strange to many parents, too. Chatters love to use abbreviations(缩写)such as: atb-all the best, bbfn-bye bye for now, cul8er-see you later, gr8-great, Idk-I don’t know, imbl-it must be love, kit-keep in touch, paw-parents are watching, lol-laugh out loud, xlnt-excellent!

It seems like another language, and it is!

小题1:The passage is meant for         .

A.children

B.parents

C.teachers

D.net bar owners小题2:Which of the following will the author probably agree with?

A.The Internet is no good for children.

B.The chat language is strange to adults.

C.Children shouldn’t chat so much online.

D.The Internet is a good place for children.小题3:In order to keep children safe online, you’d better         .

A.choose suitable websites and chat rooms for them

B.teach them to use correct net words

C.surf the Internet together with them

D.forbid them to use the Internet小题4:If you stand beside him when your son is chatting about something secret online, he may use         .

A.bbfn

B.lol

C.paw

D.cul8er

单项选择题