最新-下学期八年级物理下册第9章《压强》+教案名师优秀教案.doc
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1、(2012-2013下学期)八年级物理下册第9章压强 教案第九章 压强 第一节 压强(第一课时) (一) 学习目标 1、知识与技能目标 (1)了解压强的概念。理解什么是压力,什么是物体的受力面积。 (2)理解压强的大小跟哪些因素有关。了解增大或减小压强的主要方法。 (3)了解压强公式中的各物理量的名称、单位及符号,知道压强的单位。 2、过程与方法目标 观察生活中各种跟压强有关的现象了解对比是提高物理思维的基本方法。探究压力的作用效果跟什么因素有关,经历探究的主要环节,通过探究实验,观察实验现象、采集的实验数据,获得对压强比较深入的了解,初步学习使用控制变量法。 3、情感态度与价值观目标: (1
2、)经历观察、实验以及探究等学习活动,培养尊重客观事实、实事求是的科学态度 (2)通过亲身的体验和感悟,获得对压强、浮力基本知识理解的感性认识,为深入理解和应用这些知识打基础。 (3)通过探究性物理学习活动,获得成功的愉悦,培养参与物理学习活动的兴趣,提高学习的自信心。 (1) 感悟科学是人类创造发明的基础,激发学习热情。 (二)教学重难点 1、重点:压强概念的理解( 2、难点:压力与重力面积的正确理解( (三)教具准备 压力小桌、泡沫塑料、砝码、橡皮泥、木条、弹簧测力计 (四)教学过程 一、引入新课 1(观察教材中P两幅精美的图片:小小的蝉可以把口器插入坚硬的树皮,体态庞大66的骆驼却可以凭借
3、宽大的脚掌成为沙漠之舟( 2(同学们自己分别用笔尖和笔帽扎手,体验有什么不同的感觉( 从同学们看到的、听到的、感觉到的这些现象中,大家会想到什么问题吗? 二、进行新课 蝉为什么可以将尖尖的口器插入坚硬的树皮中? 用笔尖扎手会感到很疼,蝉的口器能插入很硬的树皮中,是因为笔尖和蝉的口器都很尖。 1、压力 请同学们分析,人站在地面上、板擦或粉笔盒放在水平的桌面上时,人对地或粉笔盒桌面的作用力的情况( 人站在水平地面上,对地面有一个向下的作用力,扳擦或粉笔盒放在水平桌面上时对平桌面也有向下的作用力,作用力的大小应等于物体的重量( 当我们要将钉子钉人墙面或将一枚图钉按在墙上(也可请一名同学演示,感觉)时
4、(钉子对墙面的作用力的情况又是怎样的呢? 按图钉或钉钉子的时候(钉对墙面有垂直于墙面的作用力( 讨论:刚才谈到的几种力的情况,它们有共同的地方吗? 我们把这种垂直压在物体表面上的力叫压力( accountable for the violation, Had a negative impact on society. Corrective measures: (LED Leadership: Luo Mingjun, rectification time: before September 25th, insist for a long time) 1, the initiative to a
5、ccept social supervision. Give full play to the role of the news media, widely publicized safety production areas to carry out the four winds special significance, focus, work measures, dynamic work, the report published telephone. Launched the employees and the whole social supervision and reportin
6、g production safety and harm the interests of the masses, the formation of a strong prevention and treatment of the special rectification work atmosphere. 2, enhance political concentration. To strengthen the ideological and political construction, always adhere to the correct political line, politi
7、cs Governance position, political orientation, political road, continuously enhance political acumen and political discernment, firm road confidence, theory system of self-confidence and self-confidence. To further strengthen the theory of armed Marx doctrine of Chinese consciously use the latest ac
8、hievements of the armed mind, guide practice and promote the work. With a high degree of political consciousness, the Bureau take the lead in-depth study to implement the spirit of general secretary Xi Jinpings important speech series, and timely to the cadres and workers to study and implement of s
9、pecial supervision and inspection. 3, focus on remediation Yung lazy, scattered. Cadres and carry out mediocre, lazy, scattered special rectification action, strengthen dedication, strong quality, The tree image, team spirit and the socialist core values education, vigorously to create a pioneering
10、spirit, unity and struggle, serious and lively atmosphere. Take a thorough investigation, and severely punish free, absenteeism, tardiness, AWOL behavior, and resolutely put an end to work time on the Internet stocks, playing games, watching entertainment phenomenon. (five) are failing to buck passi
11、ng the problem of lack of awareness of the overall situation. The individual members of the team too much emphasis on personal interests and the interests of small groups, prior conditions, the first hit small abacus. The lack of big talk about the principle of small speaking style, have something t
12、o say, not behind talking about, no more Tricks of consciousness and self-discipline, relegates, passing each other, not unite to form a good atmosphere, and sometimes even against each other. A few members of the team that is the power sector in the safety supervision department, safety supervision
13、 department is working to better cope with personal interests, perfunctory in the daily supervision process, the illegal behavior of enterprise there do not want to offend people speak hard, to relax the stringent requirements of the enterprise. The rectification measures: (LED Le 静止在斜面上或从斜面滑下的物体( 请
14、同学们分析物体对斜面的压力( 板画下面几种情况的压力 a(粉笔盒对桌面的压力( b(物体对斜面的压力( c(按图钉时图钉对墙的压力( 通过分析学生应明确,有些压力是由于重力的作用产生的(但大小并不一定都等于重力,只有放在水平面上的物体对支持面的压力大小才等于重力(在很多情况下压力和重力无关,压力不是重力( 探究压力的作用效果和什么因素有关? 猜想1:力越大产生效果越明显(因此压力的作用效果和力的大小有关( 猜想2:用笔尖和笔帽扎手时(用的力差不多大(可用笔尖扎得很痛(而笔帽则没有什么感觉,说明压力的作用效果和力的大小无关。而是和力作用的面积有关( 猜想 研究物理问题最好的方法就是实验(大家可以
15、通过实验来验证,请同学们选择合适的器材自己设计并进行实验( (同学们分组活动(教师巡视并参与学生们的活动(最后进行交流) 参考教材P图13(13的方法设计实验( 67(1)准备三块完全相同的橡皮泥(将橡皮泥编号)和两根完全相同的细木条( (2)将一根细木条放在1号橡皮泥上(通过挂有1个钩码的弹簧测力计使木条对橡皮泥产生压力( (3)取下l号橡皮泥,换上2号橡皮泥(弹簧测力计上挂上2个钩码(重做上面实验( (4)取下2号橡皮泥换上第3号橡皮泥(将两根木条放在橡皮泥上,重复实验(3) 比较三块橡皮泥的形变情况(和第一组的结论相同( 我们组分别用完全相同的两块橡皮泥(三根木条时挂4个钩码;一根木条时
16、挂2个钩码模拟了教材中“猜一猜”的内容(发现一根本条挂2个钩码时橡皮泥的压痕较深,形变较大,说明压力的作用效果更明显( 、压强 2从刚才探究过程可知,压力的作用效果既与压力大小有关,也与压力的受力面积有关。我们物理上把压力的作用效果叫压强。 物体在单位面积上受到的力叫做压强( 压力F压强的计算公式:压强, (p, ) 受力面积S符号的意义及单位: 2在国际单位制中,力的单位是牛顿(N),面积的单位是平方米(m)(由公式确定压强的2单位就是牛顿每平方米(N/m)(人们给压强规定了一个专门的单位叫帕斯卡,简称帕(Pa),这是为了纪念法国科学家帕斯卡在物理学方面作出的杰出贡献( 帕斯卡是一个很小的单
17、位,实际中还常用千帕(kPa),兆帕(MPa) (五)小结 (六)作业 附:课后总结 accountable for the violation, Had a negative impact on society. Corrective measures: (LED Leadership: Luo Mingjun, rectification time: before September 25th, insist for a long time) 1, the initiative to accept social supervision. Give full play to the role
18、 of the news media, widely publicized safety production areas to carry out the four winds special significance, focus, work measures, dynamic work, the report published telephone. Launched the employees and the whole social supervision and reporting production safety and harm the interests of the ma
19、sses, the formation of a strong prevention and treatment of the special rectification work atmosphere. 2, enhance political concentration. To strengthen the ideological and political construction, always adhere to the correct political line, politics Governance position, political orientation, polit
20、ical road, continuously enhance political acumen and political discernment, firm road confidence, theory system of self-confidence and self-confidence. To further strengthen the theory of armed Marx doctrine of Chinese consciously use the latest achievements of the armed mind, guide practice and pro
21、mote the work. With a high degree of political consciousness, the Bureau take the lead in-depth study to implement the spirit of general secretary Xi Jinpings important speech series, and timely to the cadres and workers to study and implement of special supervision and inspection. 3, focus on remed
22、iation Yung lazy, scattered. Cadres and carry out mediocre, lazy, scattered special rectification action, strengthen dedication, strong quality, The tree image, team spirit and the socialist core values education, vigorously to create a pioneering spirit, unity and struggle, serious and lively atmos
23、phere. Take a thorough investigation, and severely punish free, absenteeism, tardiness, AWOL behavior, and resolutely put an end to work time on the Internet stocks, playing games, watching entertainment phenomenon. (five) are failing to buck passing the problem of lack of awareness of the overall s
24、ituation. The individual members of the team too much emphasis on personal interests and the interests of small groups, prior conditions, the first hit small abacus. The lack of big talk about the principle of small speaking style, have something to say, not behind talking about, no more Tricks of c
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