1、国际米原器的两件复制品,测 量,实验探究的重要环节,2,学习目标,1.学习使用刻度尺，了解零点（零刻度线）、分度值、量程等概念。2.了解误差，练习多次测量求平均值减小误差的方法。学习记录、分析、表的数据和结果。3.通过一些实例练习测量长度的方法。训练使用测量工具的规范操作。,自学指导,1.阅读课本，能说出常用的长度测量工具是什么？ 2.测量前，应注意观察刻度尺的哪些内容？ 3.测量长度应注意哪些问题？ 4.什么是误差？误差和错误有什么区别？ 怎么减小误差？（8分钟后交流）,1、常用的测量工具是 。,刻度尺,一、长度测量工具,2、其它长度测量工具还有游标卡尺、千分尺等。,二、正确使用刻度尺,观察
2、：,单位,零刻度线,量程,cm,观察：,二、正确使用刻度尺,认清刻度尺的单位、零刻度线的位置、量程、分度值.,观察：,分度值,二、正确使用刻度尺,选尺：,例如:现有卷尺(分度值1cm)和卡尺(分度值0.1mm)根据需要选择测量下述物体所用的工具:1、测量跳远长度需用_.2、测量铜丝的直径需用_.,在实际的测量中,并不是分度尺越小越好,测量时应先根据实际情况确定需要达到的程度,再选择满足测量要求的刻度尺.,卷尺,卡尺,二、正确使用刻度尺,放对：,错的,二、正确使用刻度尺,放对：,零刻度线或某一数值刻度线对齐待测物的起始端，使刻度尺有刻度的边贴紧待测物体，与所测长度平行，不能倾斜。,二、正确使用刻
3、度尺,看对：,视线与刻度尺尺面垂直。,二、正确使用刻度尺,读对：,.cm,读数时，要估读到分度值的下一位.,二、正确使用刻度尺,记对：,记录的测量结果应由准确值、估读值和单位组成。,.cm,二、正确使用刻度尺,1、估：估计物体的长度。,2、选：选择不同规格的刻度尺。,3、放： （1）一端与零刻度线对齐，（2）与待测长度平行（放正），（3）紧靠被测量的物体。,4、读： （1）视线正对刻度线；（2）估读到最小刻度值的下一位。,5、记：测量结果=准确值+估计值+单位,三、测量长度应注意的问题：,1.读出上图红色物体的长度,下一题,答 案,1.该物体的长度为,下一题,17.80cm,2.读出上图红色物
4、体的长度,答 案,下一题,上一题,2.该红色物体的长度是,12.75cm,下一题,3.读出上图红色物体的长度,答 案,下一题,上一题,3.该红色物体的长度是,3.60cm,下一题,4.读出上图红色物体的长度,答 案,上一题,4.该红色物体的长度是,8.60cm,继续,1、实验探究：每人分别用刻度尺测量同一本物理教科书的长和宽，记录在课本P13表中,四、误差,2、测量的数值和真实值之间必然存在的差异叫做误差。,误差的来源：、测量时，要用眼睛估读出最小刻度值的下一位数字，是估读就不可能非常准确。、仪器本身不准确 。、环境温度、湿度变化。,四、误差,2.误差不是错误：错误是由于不遵守测量仪器的使用规
5、则，或读取、记录测量结果时粗心等原因造成的。错误是不应该发生的，是可以避免的,注意：1.误差是不可避免的，误差不可能消除,只能尽量的减小。,四、误差,3、减小误差的方法,（1）采用精密的测量工具来减小误差；（2）改进测量方法减小误差；（3）采用多次测量取平均值减小误差。,四、误差,例题：多次测量得到课本宽为184.3mm、 184.2mm、 184.5mm、 184.4mm、则课本的宽为多少？,求平均值：,当堂训练,1.测量任何物理量都必须首先规定它的 ，在物理实验中测长度往往都需要精确些，就要估读到 的下一位。 2.常用铅笔笔芯直径大约（ ），小姆指宽约有（ ），手掌的宽大约有（ ），成年人
6、的腿长大约（ ）。2.一支新中华2B铅笔的长度大约为 （ ）17.5mm B. 17.5cm C. 17.5dm D. 17.5m 3. 用一把刻度均匀但不标准的米尺，量得一桌边长为0.987m，用标准尺量得米尺的长度为1.020m，则桌边的实际长度是（ ）1.000m B. 1.007m C. 0.985m D. 0.987m4. 四位同学用分度值为1分米的同一把刻度尺测量同一物体的长度，其中错误的测量数据是 （ ）4.5dm B. 45cm C. 0.45m D. 45mm5. 1.60106m可能是 （ ）A. 一个人的高度 B. 一本书的长度C. 一个篮球场的长度 D. 一座山的高度6
7、. 在运动会跳远比赛中，用皮卷尺测量比赛成绩，如在测量时将皮卷尺拉得太紧，则测量值会 （ ）A. 变大 B. 变小 C. 不变 D. 都有可能,http:/ 上海外围招聘 -day where there are so many little foreigners not born in this country or whose parents havent been long here. She”dreamily soliloquizing, with a glance at that lavender-smocked figure“said that, last year, she an
8、d the other members of the Akiyuhapi Camp Fire in that Pennsylvanian milling town, where she became a Camp Fire Girl, did so much voluntary work upon the public playground, largely among the little immigrants, teaching them American songs, American games, telling them stories, settling their squabbl
9、es. Well! I guess Im not going to bother her with questions about her Morning-Glory name just now. Over there where shes standing”flashing another glance at the gray auto, with two girls in it and one leaning against its silver door-knob“Id have to bray like a jackass to be heard above the music of
10、that absurd piano, perched upon a low cart. Goody!” with a sudden, excited movement of her vivid shoulders. “I shouldnt like to be that perched-up pianist. Just suppose the playground horse should take it into his head to popto danceto chase the weasel, too?”Was it any suddenly restless movement on
11、the part of that four-footed servant of the city which drew the strolling piano upon a low cart from playground to playground to thresh out music for the childrens danceswas it that which flashed the thought backward over his flicking tail, over the head of the pounding pianist seated upon a light c
12、ane chair before the lashed piano, flashed it into Sallys brain? That, or the elfin dance of sunbeams upon his stamping hoofs which, together with the popping dance-cries of the children and the louder popping of the musical instrument behind himdeliriously out of tune, toomust surely infect the sta
13、idest horse?Sally did not know which launched the apprehension, the tickling sunbeams or the restless hoofs and head. But she was used to horses. She found herself mechanically straightening up, controlling the giddy dance-spirit in her own soles, moving nearernearerto the low cart as if she could n
14、ot help it.A brilliant orange streak in the sunlight she, flecked oriole-like with black, from the velvet ribbon that lent tone to that saucy little Tam, to the black needlework stars upon the heaving girlish breast.Then all at once this human flame-bird weaving its way in and out between sets of da
15、ncing children was halted by a musical crash, brought up short on tiptoe by a screaming commotion through which rang a nightmare of treble chords wildly sustained by the pianists right hand blundering among the shrieking keys of the elevated piano, while her left arm waved on high, imploring help, t
16、he whole seeming a premature, mad finale to the popping music, to which every voice upon the playground, animate and inanimate, lent a crydiscordantly at that!The effect was so feverishly funny that Sally, who had the orioles gay spirit within her orange-smocked breast, vented a shriek as loud as an
17、y, to swell the confusion, automatically clapping her fingers to her ears.The voices of some fourscore children had popped explosively from song and shout to scare-note and shriek, a conglomerate shriek, strengthened by every foreign accent under the sun (any cry ever hurled from the crumbling Tower
18、 of Babel was nothing to it!), a shriek that hung, sustained, in air together with the rasping, squelching notes of that unfinished musical measure which seemed to tatter the air itself.“Ouch! My s-soul!” murmured Sally under her breath. “The horse! Its thehorse. He is bolting, with the piano lashed
19、 to the cart behind him. And thepoorpianist!”It needed no more. She saw the girl-musicians left arm waving, imploring, saw her rock upon the light cane chair before the instrument that was not lashed to the rocking cart; she heard the horses mutinous snort, heard it strangely echoed in dumb fashion
20、by a pair of parted childish lips near her; crowning all, she caught the terrified shriek of a small boy who clutched at his raven-black hair and what English he could muster as he started toward a sand-pile ahead, yelling, “Mine babeemine babee! Horse he go kill her; sheshe go alldeaded!”And like t
21、he flame from the cloud leaped the answering fire in Sesoolittle Camp Fire Girl!“The driverthe boy driverhe ought to be shot; hes umpiring a baseball game,” was the first distinct thought that leaped to her mind as, like an oriole on the wing, she sped across the sunlit grass in the wake of the stil
22、l rocking cart, the fiendishly howling piano, the screaming, swaying pianist. The second lightning conviction was: “Its up-hill and the horse cant really run very fast with that absurd piano behind him! Hes dancing all over the place, rather than wildly running, now!. Rolie showed mehas told me so o
23、ftenhow to stop a runaway!”Rolie was her Boy Scout brother and that gallant fourteen-year-old Scout seemed to run neck and neck with her in this crisis, whispering heart into her, advising her movements.The firefly in her eyes, soaring, golden, above consternation, has lit now upon the horses quiver
24、ing haunchon his black mane.“After all, hes only a horse; Ive not alone ridden one, but, as a Camp Fire Girl, have saddled and bridled and fed an currycombed it, too, every day for the past month!” whizzed thought, darting ahead of her as with another springy step or two her right hand has seized th
25、e carts shaft to hold on and prevent herself from falling in the supreme effort she is about to make.Her left hand, attached to a strong little wrist for a girl not yet sixteen, has snatched at the dragging reins, holding them short, is trying to pull the horses head down, turn it toward her!Only a
26、horse! And a brother-horse was such a friend of hers! The firefly bore that thought upon its wings as it wheeled above doubt, resistance, wrenching strain that was tugging her soft young arms from their socketsher feet from the solid earth.Only a horse! But a maddened horse, distracted by the shrieking ivories behind him!Her girls strength against his!Yet his rebel-crest was lowering. His lifted forelegs were uncurling, the waving hoofs that cared not what they smashed returning sanely to the sod.And,
