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《机械效率》教学设计.pdf

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1、机械效率教学设计高垚骏（安徽省宣州区新田中心初中）一、教学目标（一）知识与技能1能结合实例分析什么是有用功、额外功和总功。2明确机械效率是描述做功效率的物理量。能利用机械效率的公式进行简单的计算。3能设计实验，测定某种简单机械的机械效率。（二）过程与方法1通过探究使用动滑轮的特点，知道使用机械就要做额外功。2通过实验与讨论，认识提高机械效率的主要方法。（三）情感态度与价值观知道提高机械效率的实际意义和方法，有合理改进机械、提高效率的意识，增强将科学服务于人类的责任感。二、教学重难点本节内容由“有用功和额外功”“机械效率”两部分构成，机械效率是本节教学的重点。教学中要通过实例分析有用功、额外功和

2、总功，使学生真正认识机械效率的含义。测量滑轮组的机械效率是本节的难点。教学中要组织学生经历测量的全过程，如让学生经历组装实验装置、测量数据、得出结论的过程，激发学生的学习兴趣，同时增加他们的实践体验。重点：机械效率的概念和有关计算。难点：测量滑轮组的机械效率。三、教学策略以“利用动滑轮提升重物”为背景，提出问题：动力对绳子做功等于动滑轮提升重物所做的功吗？让学生猜测并设计实验来验证自己的猜想。学生经过数据分析后发现，动力对绳子做的功总是大于动滑轮提升物体做的功。进一步分析讨论，引出有用功、额外功和总功，以及它们之间的关系和效率的概念。通过理解、运用机械效率解决实际问题，认识到提高机械效率的两种

3、方法：减小额外功和增加有用功。在讨论了怎样提高机械效率的问题之后，把效率问题延伸到学生的学习和生活中。使学生明白只有提高学习效率才能顺利完成任务。四、教学资源准备多媒体设备、实物投影仪、动滑轮、钩码、铁架台、弹簧测力计、刻度尺、细线等。五、教学过程教学环节教师活动学生活动设计意图导入新课（5分钟）小明家最近买了一处新楼房，家在三楼。想把洗手间、厨房装修一下，需把沙子运到三楼。请同学们根据需要，选择器械帮助小明家解决这个问题，看看哪个小组选的办法最好？请学生发表自己的见解，提出各种方案。并对各个方案进行创设真实的情景，容易激发学生兴趣，顺文档编码:CR7E2K7G

4、6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I

5、4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G

6、6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I

7、4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G

8、6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I

9、4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G

10、6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3图 1 如图 1 所示的三种方法供参考：第 1 种是人直接提着沙子上楼；第 2 种是把沙子放进桶里，人通过动滑轮把沙子拉上楼；第 3 种是把沙子放进质量较小的袋子里，人通过动滑轮把沙子拉上楼。讨论，比较优缺点。经过讨论明确第一种方法太不方便。第三种方法最好，因为它比第二种方法用的力小。提升相同高度做的功少。利进入教学。通过讨论，为下面

11、学习有用功与额外功做好铺垫。文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:C

12、R7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5

13、H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:C

14、R7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5

15、H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:C

16、R7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5

17、H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3新课教学（30 分钟）一、有用功和额外功结合用动滑轮提升沙子，请同学们观看提沙子过程的视频。思考：1在把沙子从一楼运上三楼的过程中，每种方法中各对哪些物体做了功？2无论他采取哪种方法都必须做的功是他对什么做的功？3在几种不同的方法中他不愿做但又不得不做的功分别是什么？板书：一般来说，机械对外所做的功为有用功，机械克服自身部件的

18、重力和摩擦力所做的功为额外功，动力对机械所做的功为总功。总功等于有用功与额外功之和。指出：前面实验中，第三种方法最好，因为第三种方法做的额外功最少，总功最少。讨论：不使用机械直接提升物体做的功，与使用机械提升物体做的功一样吗？（手拉绳做的功与动滑轮对沙子做的功相等吗？）怎样探究这个问题？1设计实验方案：用手通过一只弹簧测力计拉一个动滑轮，沿竖直方向匀速缓慢提起重为G 的钩码。2为了探究上述问题需要测量的物理量是：手对绳进一步思考并回答。边实验边填表。分析实验进一步理解有用功和额外功。并会测量有用功和总功。文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3

19、D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3

20、 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3

21、D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3

22、 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3

23、D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3

24、 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3

25、D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3的拉力 F、手移动的距离s、钩码的重力、钩码上升的高度 h。3改变钩码的数量，重复上述测量。4设计表格，将实验数据填入表中。次数手的拉力F/N 手移动距离 s/m 钩码重G/N 钩码上升高度 h/m 1 2 3 5分析实验数据：（1）手拉绳所做的功与动滑轮拉钩码所做的功是否相等？（2）哪一个做的功多一些？（3）你认为产生这一现象的原因是什么？误差，指出要使重物重一些，误差就会小一些。（1）不相等（2）手拉

26、绳做的功多（3）有摩擦，在提起重物时还要提起动滑轮。二、机械效率工作中，我们总是希望额外功越少越好；也就是有用功在总功中所占的比例越大越好。在物理学中，用机文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K

27、7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ

28、7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K

29、7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ

30、7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K

31、7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ

32、7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3械效率表示有用功在总功中所占的比例。计算公式：三者之间的关系：注意：对于实际机械，由于总是有额外功存在，1。组织学生讨论：1.机械效率有单位吗？2为什么机械效率没有大于1 的？3用小

33、数和百分数来表达机械效率，你认为那种表达更好？通过多媒体展示例题：利用如图 2 所示的滑轮组，在 F=80N的拉力作用下,将一个重为 180N 的物体匀速举高 1m，绳重、摩擦不计。求：总功、有用功、额外功和滑轮组的机械效率。图 2 经过讨论回答：机械效率没有单位，总小于 1，用百分数表示。意在练习机械效率公式的应用、使学生加深认识有用功、额外功和总功的概念。锻炼分析实际问题的能力。通过交流与合作，培养学生团结合作精神。文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1

34、V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码

35、:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1

36、V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码

37、:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1

38、V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码

39、:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1

40、V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3（1）组织学生分析、讨论、计算（2）展示学生解题过程3）总结、评价如何测量滑轮组的机械效率：1实验原理：2器材：刻度尺、钩码、弹簧测力计、铁架台、甲、乙两个滑轮组、长约2m 的细绳。3步骤：用弹簧测力计测量钩码所受的重力G 并填入表格。分别记下钩码和弹簧测力计的位置。缓慢拉动弹簧测力计，使钩码升高，读出拉力 F 值，用刻度尺测出钩码上升的高度h 和弹簧测力计移动的距离 s，将这三个量填入表格。算出有用功 W 有用、总功 W 总功、机械效率并填入表格。实验次数G (N)h(m)W 有

41、用（J）F(N)s(m)W 总（J）1 2 学生动手实验理论联系实际，培养学生将科学知识应用于日常生活和社文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7

42、ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E

43、2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7

44、ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E

45、2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7

46、ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E

47、2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J33 4 结论：1动滑轮重一定,物重越大，机械效率高。2物重一定，动滑轮越重，机械效率低。讨论：如何提高滑轮组的机械效率？讨论后得出：提高滑轮组的机械效率的主要方法有：尽可能地增加物重，减小动滑轮重，减轻绳重和滑轮转轴处

48、的摩擦。会实践的意识。课堂小结（5分钟）让学生分组讨论，总结本节学到了什么知识，有哪些收获？学生自己归纳总结，分小组发言，教师对学生归纳发言较好的给予表扬，并指出其中的不足。让学生有表现自我的机会，并且发现学习过程中出现的问题。文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编

49、码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S

50、1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编码:CR7E2K7G6H3 HW2M1S1V5H7 ZZ7I4E3D8J3文档编

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关键词：: 机械效率教学设计

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本文标题：《机械效率》教学设计.pdf
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