如图所示,水平光滑地面上停放着一辆小车,左侧靠在竖直墙壁上,小车的四分之一圆弧轨

题型:计算题

问题:

如图所示,水平光滑地面上停放着一辆小车,左侧靠在竖直墙壁上,小车的四分之一圆弧轨道AB是光滑的,在最低点B与水平轨道BC相切,BC的长度是圆弧半径的10倍,整个轨道处于同一竖直平面内。可视为质点的物块从A点正上方某处无初速下落,恰好落入小车圆弧轨道滑动,然后沿水平轨道滑行至轨道 末端C处恰好没有滑出。已知物块到达圆弧轨道最低点B时对轨道的压力是物块重力的9倍,小车的质量是物块的3倍,不考虑空气阻力和物块落入圆弧轨道时的能量损失,求:

(1)物块开始下落的位置距水平轨道BC的竖直高度是圆弧半径的几倍;

(2)物块与水平轨道BC间的动摩擦因数μ。

考点:机械能守恒定律动能定理动量守恒定律的应用
题型:计算题

下列标本中哪个为下呼吸道感染病原学诊断的理想标本().

A.鼻拭子

B.痰

C.咽拭子

D.通过气管收集的标本

E.唾液

题型:计算题

阅读理解。

     I was giving the class when her giggling drew my attention. Walking over to the young troublemaker, I

asked for the note in her hands.

     It was a hand-drawn picture of me, teeth blackened, nostrils (鼻孔) upwards, and the words "I'm stupid"

coming out of my mouth. I managed to fold up the picture calmly and continue the class. My mind, however,

was working angrily. I knew the two most likely suspects for drawing the picture. Maybe it was high time

that I taught them a lesson!

     Somehow, in the very moment of real hurt and anger, I asked myself very softly, "How can I ever bring

good out of this?"

     When there were about six minutes left of the class, I showed the kids the picture. The whole class was

silent. I told them there must be a reason behind such a picture and that now was their chance to tell me the

reason. Then I let them write silently while I stood sadly in the back of the classroom.

     Most of them either blamed the artist or felt sorry. But two notes, from the girls I figured were behind the

picture, had a list of issues. I was too mean and too strict. Reading those notes, I realized that where I thought

I was driving them to success I was actually driving them away. I had some apologizing to do.

     When the kids walked into my classroom the next day, one boy and one girl each handed me a card. The

one signed by all the boys expressed sincere regret for the ugly joke. The one from the girls asked for

forgiveness. I was extremely surprised and more than a little shameful. I had my little speech all ready to give

to the kids, but they did it before me.

1. What caused the girl to giggle?

A. The funny look of the teacher.

B. The teacher's interesting lecture.

C. The funny picture about the teacher.

D. The short story written on the note.

2. Why did the teacher give up punishing the students who drew the picture?

A. Because she didn't want to stop in the middle of the class.

B. Because she didn't exactly know who drew it.

C. because she didn't think it would do any good.

D. Because the students' apology removed her anger.

3. The main reason for the students' complaints was that the teacher _____.

A. was too strict with them

B. didn't five interesting lessons

C. didn't treat them equally

D. was not kind to them

4. What does the passage mainly tell us?

A. Forgiving others is actually helping yourself.

B. It is not right to push students too hard.

C. Teachers should get along well with students

D. Teachers should respect students' choices

题型:计算题

经过验证的对产品设计、质量标准和生产、技术、质量管理进行全面描述的基准性技术文件是

A.二冬
B.二术
C.二母
D.二活
E.二枫藤上述药物分别是指

题型:计算题

在分析了目标人群的信息需求和媒体材料需求之后,就需要确定向目标人群()。

A.传播健康知识

B.传播具体信息

C.提供保健技能

D.提供传播资料

E.传播的有效方式

题型:计算题

( )建设项目信息门户有严格的数据安全保证措施,用户通过一次登录就可以访问所有规定权限内的信息源。

A.建设项目协同工作层

B.个性化设置层

C.工作流支持层

D.数据安全层

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