如图所示,AB是一质量为m的均匀细直杆,A端靠在光滑的竖直墙壁上,B端置于水平地

题型:选择题

问题:

如图所示,AB是一质量为m的均匀细直杆,A端靠在光滑的竖直墙壁上,B端置于水平地面上,杆身与竖直方向夹角为θ,杆与地面的摩擦系数为μ,保持平衡,则此时杆与地面的摩擦力为(  )

A.mgtgθ

B.mgsinθ

C.μmg

D.μmg

考点:摩擦力的大小摩擦力的种类杠杆的平衡条件
题型:选择题

下列情况中的物体,哪些可以看作质点(  )

A.研究从北京开往上海的一列火车的运行速度

B.研究正在做课间操的同学们

C.研究原子的内部结构时的原子

D.观察航空母舰上的舰载飞机起飞时的航空母舰

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Put on your sunglasses and enjoy the island, the sun and the blue sea. Malta combines (结合) learning English with the Mediterranean way of life: you will have a language course and a great holiday at the same time.
Your language course
Our school lies in Sliema, only a few meters from the sea, the beach road and cafés. The school is in an old Maltese building. Our teachers use a modern teaching method and you will learn English quickly.
Brief information
Class size: 10, at most 15 students
Minimum (最小) age: 13
Language levels: all
Internet access: in the Internet cafe
The leisure (休闲) programmes
Our school and team leaders organize varied leisure programmes. There will be a welcome party on your first day. You will also take part in beach volleyball, and beach parties.
Other activities include: Discos, visit to Popeye Village, Water Park, bowling, cinema, ice skating (different prices).
Accommodation
Family: You will live in friendly host families that the school has known for years. All families are near the school (20 minutes on foot or by bus).
Supervision (监督)
Our team of friendly teachers, team leaders and host families will always be there for you. There is also an emergency phone number for parents and students.
Dear parents, please note that there are periods of time when your children are unsupervised, for example on the way to school. We are happy to discuss any questions you may have. Please contact us by phone or email.
小题1:If you want to attend the English course in Malta, you should ______.
A.be at least 13 years oldB.have a higher English level
C.learn English without the InternetD.be watched all the time
小题2:Where will you live if you attend the English course in Malta?
A.In an old Maltese building.B.In a local family.
C.In a café in Sliema.D.In Popeye village.
小题3:What information can you get from the passage?
A.There are at least 15 students in a class.
B.You can take part in any activity for free.
C.You will have a good time while learning English.
D.It takes you 20 minutes to go to school by bus.
小题4:The passage is mainly written for ______.
A.travelers to MaltaB.teachers planning to work abroad
C.host families wishing for studentsD.teenagers learning English
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新课程要求教师提高素质、更新观念、转变角色,教师的教学行为也就要产生相应的变化,根据你的理解,新课程中教师的教学行为将发生哪些变化?(湖南省)

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股份有限公司与独资企业和合伙企业相比具有对公司收益重复纳税的缺点。()

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测定土的抗剪强度指标的试验方法主要有()

A.室内剪切试验

B.现场剪切试验

C.室外剪切试验

D.室内剪切和现场剪切试验

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