问题 选择题

鹏程同学要在客厅里挂上一幅质量为1.0kg的画(含画框),画框背面有两个相距

1.0m、位置固定的挂钩,他将轻质细绳两端分别固定在两个挂钩上,把画对称地挂在竖直墙壁的钉子上,挂好后整条细绳呈绷紧状态,如图所示,设细绳能够承受的最大拉力为10N,g取10m/s2,则细绳至少需要多长才不至于断掉(  )

A.

2
3
3
m

B.

3
3
m

C.

2
m

D.1.0m

答案

以画框为研究对象,分析受力情况,作出力图.设细绳最短时两绳的夹角为2α,此时两细绳的拉力达到最大值,即F=10N,根据平衡条件得:

2Fcosα=mg

代入解得:cosα=

1
2
 即:α=60°

为了细绳不被拉断,细绳最短的长度为L=2

0.5
sin60°
m=
2
3
3
m

故选A

完形填空

任务型阅读(本题共5小题,每小题2分,共10分)

Life in the future will be different from life today. Between then and now many changes will take place, but what will the changes be?

The population is growing fast. There will be many people in the world and most of them will live longer than people live now.

Computers will be much smaller and more useful, and there will be at least one in every home. And Computer Studies lessons will be one of the most important subjects in schools then.

People will work _______ hours than they do now and they will have _____ free time for sports, watching TV and travel. Traveling will be much cheaper and easier. And many more people will go to other countries for holidays.

There will be changes in our food, too. More land will be used for building new towns and houses for all the people. Then there will be less room for cows and sheep, so meat will be more expensive. Maybe no one will eat it every day. Instead they will eat more fruit and vegetables. Maybe people will be healthier.

Work in the future will be different, too. Dangerous and hard work will be done by robots. Because of this, many people will not have enough work to do. This will be a problem.

小题1:在文中空格处填上适当的词 _____________ ______________

小题2: 将划线句子译成汉语_________________________________________________

小题3:找出同义句: Every family will have one computer or more.

________________________________________________________________________

小题4: 回答问题:What will be one of the most important subjects?

____________________________________________________________________

小题5:找出或写出本文的主题句_________________________________________________

判断题