如图所示,水平面B点以左是光滑的,B点以右是粗糙的,质量为m1和m2的两个小物块

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问题:

如图所示,水平面B点以左是光滑的,B点以右是粗糙的,质量为m1和m2的两个小物块,在B点以左的光滑水平面上相距L,以相同的速度向右运动.它们先后进入表面粗糙的水平面后,最后停止运动.它们与粗糙表面的动摩擦因数相同,静止后两个质点的距离为x,则有(  )

A.若m1>m2,x>L

B.若m1=m2,x=L

C.若m1<m2,x>L

D.无论m1、m2大小关系如何,都应该x=0

考点:匀变速直线运动的位移与时间的关系牛顿第二定律
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To most of us, school means classes, teachers, schedules, grades, and tests. But for the children at Sudbury Valley School in Massachusetts, school is very different.

Firstly, there are no lessons. All the children, aged between 4 and 19, do whatever they want. There are no teachers, only “staff members (职员)”. The idea behind this is that you do not need to make children learn, because children want to learn anyway. “You do not need to say to a three-year-old. ‘Go explore your environment.’ You can’t stop them!” says Daniel Greenberg, a founder of the school. “But if you make children do what you want all day, they will lose all taste for learning.”

At Sudbury Valley School, you will allow children to talk, read, paint, cook, work on computers, study French, play the piano, climb trees, or just run around. Two boys spent three years just fishing!

The other way that Sudbury Valley School is different is that the children can decide the rules. Every week, there is a school meeting where both children and staff have one vote each — even the four-year-olds. They decide the school rules, how to spend the school budget(预算), and even which staff they want and do not want any more.

When the school first opened in 1968, people said it would never work. But today, the school has 200 students, and 80% of its students go on to college. Even the two boys who went fishing all time have successful careers today. One of them is a musician and the other is a computer scientist.

小题1:What does the school believe?

A.Teachers cannot teach children well.

B.Children learn best when they do what they want to do.

C.Learning is for adults — children should only play.

D.Children should only learn about one thing at a time.小题2:What does Daniel Greenberg say about three-year-olds?

A.They love learning.

B.They are very naughty.

C.They want to be outside all the time.

D.They are too young to learn anything.小题3:What happens to the children after they leave this school?

A.They do the same things as children from other schools.

B.They have problems getting into college or getting a job.

C.They usually do very unusual jobs.

D.They are not successful in their business.小题4:What is the main topic of the article?

A.Children’s hobbies

B.Education in the US

C.A school without rules

D.An unusual school

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各级疾病预防控制机构承担传染病监测、预测、流行病学调查、疫情报告以及其他预防、控制工作。()

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下列哪一个不是企业采购过程的要素()。

A.订购货物入库管理

B.确定订货种类

C.订单跟踪

D.填写订购申请

题型:选择题

运行以下程序段后,输出结果为 【13】 。 For I=1 TO 3 Cls Print "I=",I; Next

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某中学一历史研究小组对德意志帝国的“君主立宪制”进行探究,有同学提出“为什么说德意志帝国的君主立宪制是一种不彻底不完善的代议制”,对这个问题,有四位同学产生了争议。你认为他们的回答当中最正确是()

A.甲同学:皇帝和帝国宰相掌握行政大权

B.乙同学:联邦议会权力较大,帝国议会权力较小

C.丙同学:行政机构权力大,立法机构权力小

D.丁同学:行政机构控制了立法机构

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