测定木块与长木板之间的动摩擦因数时,采用如图甲所示的装置,图中长木板水平固定.

题型:问答题

问题:

测定木块与长木板之间的动摩擦因数时,采用如图甲所示的装置,图中长木板水平固定.

(1)实验过程中,电火花计时器应接在电压为______V,频率为50Hz的交流电源上;

(2)如图乙为木块在水平木板上带动纸带运动时打出的一条纸带的一部分,0、1、2、3、4、5、6为计数点,相邻两计数点间还有4个打点未画出,从纸带上测出x1=7.22cm,x2=15.52cm,则木块加速度大小为a=______m/s2(保留两位有效数字);

(3)已知重力加速度为g,测得木块的质量为M,砝码盘和砝码的总质量为m,木块的加速度为a,则木块与长木板间动摩擦因数μ的表达式为______;

(4)若实验操作规范,数据处理方法得当,由此算得的动摩擦因数将比真实的动摩擦因数______(请填写“偏大”、“偏小”或“相同”).

考点:滑动摩擦力、动摩擦因数
题型:问答题

       新闻媒体经常报道有关中东的消息:频繁的冲突、战争给这里的人民带来了深重的灾难。试分析其原因。

                                                                                                                                                              

                                                                                                                                                              

题型:问答题

现行的《地表水环境质量标准》(GB3838-2002)中,Ⅲ类水的BOD5标准限值为()。

A.≤4mg/L

B.≤6mg/L

C.≤8mg/L

D.≤10mg/L

题型:问答题

测试的目的是暴露错误,评价程序的可靠性;而______的目的是发现错误的位置并改正错误。

题型:问答题

Ⅲ. 阅读理解(共两节,满分40分)

第一节:阅读理解(共15小题;每小题2分,满分30分)

阅读下列短文,从每题所给A、B、C和D项中,选出最佳选项,并在答题卡上将该项涂黑。

In order to know a foreign language thoroughly(完全地), four things are necessary. First, we must understand the language when we hear it spoken. Secondly, we must be able to speak it ourselves, correctly with confidence(自信) and without hesitation(犹豫). Thirdly, we must be able to write it. We must be able to make sentences that are correct in grammar.

There is no short way to succeed in language learning. A good memory(记忆) is a great help, but it is not enough only to memorize the rules from a grammar book. It is no much use learning by heart long lists(一览表) of words and their meanings, studying the dictionary and so on. We must learn by using the language. If we are pleased with a few rules we have memorized, we are not really learning the language. We must “Learn through use”. Practice is important. We must practise speaking and writing the language whenever(无论何时) we can.

1.The most important things to learn a foreign language are __________.

A.understanding and speaking              B.hearing, speaking, reading and writing

C.writing and understanding                D.memorizing and listening

2.Someone hears and writes English very well, but he speaks it very badly. This is because __________.

A.he doesn’t understand the language when he hears it spoken

B.he doesn’t have a good memory

C.he always remember lists of words and their meanings

D.he often hesitates to practise speaking it

3.One can never learn a foreign language well only by __________.

A.much practice                                B.studying the dictionary

C.learning through use                        D.using the language

4.Which of the following is the most important in learning a foreign language?

A.A good memory.     B.Speaking.           C.Practice.             D.Writing.

5.“Learn through use” means __________.

A.we use a language in order to learn it

B.we learn a foreign language in order to use it

C.we can learn a language well while we are using it

D.both B and C

题型:问答题

纹泥的成因是()的沉积作用。

A、片流,

B、河流,

C、海洋,

D、冰水

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