奇穴

电算化系统中备份功能是重要的基本功能，进行这一工作时应（）。

A.注明备份时间

B.先恢复数据

C.删除数据前必须先备份

D.备份软盘应有多份

在实验室用两端带竖直挡板C、D的气垫导轨和有固定挡板的质量都是M的滑块A、B，做“验证动量守恒定律”的实验，实验步骤如下：

（1）把两滑块A、B紧贴在一起，在A上放质量为m的砝码，置于导轨上，用电动卡销卡住A、B，在与A、B的固定挡板间放入一弹簧，使弹簧处于水平方向上压缩状态.

（2）按下电钮使电动卡销放开，同时起动两个记录两滑块运动时间的电子计时器，当A、B与挡板C、D碰撞时，电子计时器自动停止，记下A至C运动时间t，B至D运动时间t₂.

（3）重复几次取t₁、t₂的平均值.

①在调整气垫导轨时应注意______________________________________________________；

②应测量的数据还有____________________________________________________________；

③只要满足关系式________________________________________成立，即可验证动量守恒.

当S≤1.64N的区域属于超声波的（）。

按要求画图。

（1）画出小球的受力情况；

（2）木块与斜面粗糙，木块沿斜面匀速下滑，画出木块的受力情况。

Do you love your family? Then May 15, the International Day of Families, was a good day to celebrate! The United Nations started this special day in 1994. it wanted people to know how important families are. If all the families on Earth could be happy, then the whole world would be a more peaceful place.

What makes a happy family? Our readers say it’s understanding!

Zhao Wei, 15, girl, Harbin Lianzhong Middle School: “My parents seldom fight with each other. I quarrel with them sometimes. They think I should not make friends with some kids who think they are bad. I think I’ve grown up and can make my own decisions. But most of the time, my parents are right. To me, family is like a soft sofa. I can be very comfortable on it!”

Wu Hao, 14, boy, Nanjing Foreign Language School: “My family is not rich. When I was a small child, other kids had a lot of good stuff (东西) but I didn’t. I asked my parents why. They told me that we didn’t have much money. I began to understand my parents then. I will do part-time jobs when I enter college. That way my parents won’t have to work so hard. Family is like a nest. It’s warm and safe.”

Zhang Xun, 15, boy, Hefei No 45 Middle School: “I’m a naughty boy who doesn’t study very hard. My parents always talk to me about this and they get very angry sometimes. I hope they won’t get angry when they talk to me. And I should behave well and be a good boy. My family is like my basketball. I love playing basketball. It makes me happy.”

46. People have celebrated the International Day for _________ years.

A. more than 19   B. about 15   C. less than 15    D. just 8

47. The United Nations started the International Day mainly _______.

A. to amuse people               B. to get people to know families are important

C. to make people a peaceful world  D. to make people who have families happy

48. Zhao Wei sometimes quarrels with her parents because _______.

A. she has grown up                B. she enjoys making friends with kids

C. they stop her from making friends   D. her parents are always right

49. Wu Hao will _________ when he enters college.

A. do part-time jobs to make his parents relaxed

B. make his family warm and safe

C. work to buy a lot of good stuff

D. do part-time jobs to get some money

50. Zhang Xun _______.

A. likes his family very much

B. likes his family if his parents let him play basketball

C. hates his family because his parents don’t like him

D. hates his family because his parents always get angry with him