问题 问答题

(1)为了探究加速度与力、质量的关系,某实验小组设计如图甲所示的实验装置:一个木块放在水平长木板上,通过细线跨过定滑轮与重物相连,木块与纸带相连,在重物牵引下,木块在木板上向左运动.重物落地后,木块继续向左做匀减速运动,打出的纸带如图1所示,每隔一点取一个计数点(不计纸带所受到的阻力,交流电频率为50Hz,重力加速度g取10m/s2)(②③问结果保留一位小数)

①两计数点之间的时间间隔为______s

②木块减速阶段的加速度为______m/s2

③木块与木板间的动摩擦因数μ=______

(2)二极管是电子线路中常用的电子元件.它的电路符号如图2甲所示,正常使用时,“+”极一端接高电势,“-”极一端接低电势.要描绘某二极管在0~8V间的伏安特性曲线,另提供有下列的实验器材:电源E(电动势为8V,内阻不计):多用电表电压档有五个量程,分别为2.5V、10V、50V、250V、500V,可视为理想电压表);开关一个;滑线变阻器一个;mA表一块;导线若干.

①在答题纸对应的方框内画出测定二极管伏安特性的电路原理图,多用电表在电路图中用V表示,并注明电压表挡所选量程.

②利用多用电表电压档测量正常使用中的二极管电压时,电流从______(选填“红”或“黑”)表笔流入电表.

③某同学通过实验得出了图2乙所示的伏安特性曲线图.接着,他又用该二极管、电源E和另一只固定电阻R等组成图2丙所示的电路,当闭合开关后,用多用电表的电压挡测得R两端的电压为0.8V,由此可以判断固定电阻R的阻值大约为______Ω.

答案

由给出的数据可知,重物落地后,木块在连续相等的时间T内的位移分别是:

s1=7.72cm,s2=7.21cm,s3=6.71cm,s4=6.25cm,s5=5.76cm,s6=5.29cm,s7=4.81cm,s8=4.31cm

以a表示加速度,根据匀变速直线运动的规律,有

a=

(s5-s1)+(s6-s2)+(s7-s3)+(s8-s4)
16T2

又知T=0.04s

解得:a=-3.0m/s2

重物落地后木块只受摩擦力的作用,用m表示木块的质量,根据牛顿第二定律有:

-μmg=ma

解得μ=0.30

(2)①如图所示:

②红正黑负,红表笔连接表头的正接线柱,故电流从红表笔流入;

③当电压为0.8V时,由I-U图象到电流约为0.01A,故电阻约为80欧姆;

故答案为:(1)①0.04;②3.0;③0.3;(2)①如图所示; ②红; ③80.

完形填空

第二节 完形填空(共20小题;每小题1.5分,满分30分)

阅读下面短文,从短文后各题所给的四个选项(A、B、C和D)中,选出可以填入空白处的最佳选项,并在答题卡上将该项涂黑。

A man’s best friend may become his enemy. His children that he has_____16____with loving care may show no thanks. Those who are ____17_____to us, those whom we trust with our happiness____18_____turn against their faith. The money that a man has, he may___19_____.It flies from him, perhaps when he needs it _____20______.A man’s reputation(名誉) may be lost in a moment of ill-considered_____21_____. The people who would prefer to fall on their knees to do us honour when success is with us may be ____22____ to throw the stone malice(敌意) when failure settles upon our heads.

The one absolutely(绝对地)____23_____friend that man can have in this selfish world, the one that never deserts(遗弃) him is his_____24_____. A man’s dog stands by him____25____he is rich or poor, healthy or sick. He will sleep on the cold ground,____26_____the wintry winds blow and the snow drives hard,____27____he may be near his master’s side. He will _____28____the hand that has no food to offer. He guards the sleep of his poor master as if he ___29_____ a prince. When all other friends desert him , the dog_____30____. When reputation falls to pieces, he is as constant(不断的) in his love as the sun in its journey _____31_____the heavens.

If the master becomes friendless and homeless,____32____the faithful dog asks for is to be with him. And when___33___ takes his master in its embrace(拥抱) and his body____34___away in the cold ground, there by the graveside(墓边) will the dog be found, his head between his paws, his eyes sad but ____35______in watchfullness, faithful and true even in death.

16. A. brought out   B. brought up        C. brought in       D. brought on

17.  A. nearest       B. most useful        C. most important   D. strangest

18.  A. must         B. have to           C. may            D. should

19  A. keep         B. Use             C. earn            D. lose

20.  A. more        B. most             C. better           D. very

21.  A. action       B. thought           C. movement       D. mind

22.  A. first         B. last              C. latest           D. newest

23.  A. close       B. selfish           C. kind             D. unselfish

24.  A. wife         B. dog             C. himself          D. brother

25.  A. whether      B. even though      C. although         D. whenever

26.  A. there        B. because          C. where          D. which

27.  A.as long as     B. even if          C. so that           D. though

28.  A. eat          B. take            C. kiss             D. shake

29.  A. is           B. were            C. had been        D. would be

30.  A. leaves       B. cries            C. remains         D. disappears

31.  A  into        B. on              C. out of          D. through

32.  A. why         B. which           C. how           D. what

33.  A. birth        B. life              C. death          D. kindness

34.  A. lay         B. is lain            C. is laying         D. is laid

35.  A. closed       B. open            C. shut             D. Opened

判断题