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1、班级姓名科目物理年级八年级主备人编号课题第八章第二节二力平衡授课人审核人情境导入自主探究学习目标1、知道日常中常见的摩擦现象2、知道增大或减小摩擦的方法3、知道摩擦的利与弊重点探究摩擦力的大小与什么因素有关难点滑动摩擦力的定义及方向自学检测1、两个的物体,当它们之间或时,就会在接触面上产生一种阻碍物体的力,这种力就叫摩擦力。摩擦力的方向总是跟物体运动的方向。2、滑动摩擦力的大小跟大小有关,还跟有关,越大,滑动摩擦力越大;接触面越,滑动摩擦力越大。3、例举增大有益摩擦的例子:4、例举减小有害摩擦的例子:小组合作学习探究一:摩擦力的定义及种类思考:摩擦力产生的三个条件:思考 2:摩擦力的种类种类定
2、义图示简介实例静摩擦力两个相互接触的物体时产生的摩擦物体推而未动手握瓶子静止,手与瓶子之间的摩擦滑动摩擦一个物体在另一个物体表面上时产生的摩擦在粗糙的表面上推物体运动人滑冰时,冰刀和冰面之间的摩擦滚动摩擦一个物体在另一个物体上时产生的摩擦带轮小车在力的作用下运动正常行驶的自行车【例题 1】关于摩擦力,下列说法正确的是()A相互挤压的粗糙物体之间总有摩擦力B静止的物体一定不受摩擦力C相对运动的两个物体,一定存在摩擦力D一个物体只有在另一个物体表面运动或有相对运动趋势时,才有可能受到摩擦力【例题 2】下列几种情况,不属于滑动摩擦的是()A自行车刹车时闸皮和车圈之间的摩擦B用圆珠笔写字,笔尖的圆珠与
3、纸之间的摩擦C用卷笔刀削铅笔,刀与笔之间的摩擦D小孩滑滑梯,身体与滑梯之间的摩擦学生质疑:探究二:影响滑动摩擦力大小的因素1、体验:用手按在桌面上滑动,体会手的感觉:(1)学生用手压在物理封面上拖动,感受一下拖动时封面作用在手上的阻力(摩擦力)。(2)手对封面压得再紧一些,感受一下拖动时封面作用在手上的阻力。(3)然后在桌面上拖动,感受一下拖动时桌面作用在手上的阻力。感受:2、猜想:滑动摩擦力大小与什么因素有关?3、实验设计:如果想探究这些因素对摩擦力的影响,我们应该如何设计这个探究实验,请同学们参考课本 22 页的探究提示和课桌上的实验器材,设计你的实验方案。A、器材:一个弹簧测力计、一个木
4、块、一块木板、一条毛巾、钩码。B、你怎样测量出摩擦力的大小?。测量出摩擦力的大小的原理是根据了。C、在实验中我们采用了法和转化法。D、我们是怎样改变和控制变量的?E、步骤:甲、乙图是控制相同,不同,用弹簧测力计拉着木块滑动,此时,木块与木板之间的摩擦力就等于的示数。甲、丙两图是控制相同,不同,用弹簧测力计拉着木块滑动,此时的摩擦力等于的示数。假设我们猜想与接触面的面积有关,我们如如何来验证:4、进行实验,将实验数据记入表格中。文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:
5、CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F
6、1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:
7、CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F
8、1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:
9、CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F
10、1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:
11、CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3实验条件弹簧测力计的示数(F/N)压力情况接触面粗糙情况接触面面积情况甲乙丙5、分析实验数据,得出结论:滑动摩擦力的大小与有关,表面受到的压力越大摩擦力越,还跟接触面的,接触面越粗糙摩擦力越。6、讨论:想一下你的实验过程中有什么优点和不足,和同学们交流一下看法。(三)成果展示我对摩擦力的理解:【练习 1】如图所示,放在M、N 两水平桌面上的P、Q 两物体,分别在FP=5N、FQ=3N 的水平拉力作用下做匀速直线运动,可以确定()A桌面 M 一定比桌面N 粗糙BP 的速度一定大于Q 的速度C P 的质量一定大于Q 的质量DP
12、受到的摩擦力一定大于Q 受到的摩擦力学生质疑:探究三:摩擦的利用与防止1增大有益摩擦的方法:2减小有害摩擦的方法:【例题十八】关于摩擦,下列说法正确的是()A用滚动代替滑动可以减少摩擦B若水平路面无摩擦,汽车运动会加快C在机器的转动轴承上加润滑油可消除摩擦D增大有益摩擦只能采用增大对接触面压力的方法总结归纳达标检测总结拓展通过本节课的学习,谈谈你有哪些收获?课堂检测1、如图所示,物体从斜面上匀速滑下的过程中(不计空气阻力),受到的力有()A重力和支持力B重力、支持力和下滑力C重力、下滑力和摩擦力D重力、支持力和摩擦力2、下列几种情况,不属于滑动摩擦的是()文档编码:CY9L2I8P2E8 HE
13、7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U
14、3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE
15、7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U
16、3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE
17、7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U
18、3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE
19、7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3A自行车刹车时闸皮和车圈之间的摩擦B用圆珠笔写字,笔尖的圆珠与纸之间的摩擦C用卷笔刀削铅笔,刀与笔之间的摩擦D小孩滑滑梯,身体与滑梯之间的摩擦3、如图所示的事例中,目的是减少摩擦的是()4、一物体以1m/s 的速度在水平桌面上做匀速直线运动,受到的摩擦力为10N,若速度增大到 2m/s,仍在该水平桌面上匀速运动,它受到的摩擦力大小为(不计阻力)()A大于 10N B等于 10N C小于 10N
20、D 条件不足,无法判断5、如图所示,用水平推力推静止的水平地面上的大木箱,没有推动。这时木箱受到的()A推力小于摩擦力B推理和摩擦力大小一定相等C推力一定小于重力D推力和摩擦力方向相同6、货物如图所示随传送带一起匀速斜向上运动,除图中已画出的力外,货物还受到一个力F的作用,画出这个力的示意图。教学反思文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6
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23、ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L
24、2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6
25、ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3文档编码:CY9L2I8P2E8 HE7X5I8F1T6 ZS4M5G7A8U3
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