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1、Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3
2、.5 Client Profile 5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.等效替代 效果相同Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slides for .NET
3、 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyri
4、ght 2004-2011 Aspose Pty Ltd.1 1、合力：、合力：一个力产生的效果跟几个力共同产生的效果相同，这个 力叫做那几个力的合力。原来的几个力叫做分力。求几个力的合力的过程或方法，叫做力的合成说明：在实际问题中，就可以用这个力来代替那几个力，这 就是力的等效代替等效代替。而不是物体又多受了一个合力。2 2、力的合成：、力的合成：Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slides f
5、or .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.一条直线上的力的合成F1F2F1F=F1 + F2F2F1F=F1 - F2一个力作用二力同向二力反向Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client
6、Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.互成角度的力怎 样求合力？F1F2Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.C
7、opyright 2004-2011 Aspose Pty Ltd.探究求合力的方法探究求合力的方法思考1：Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.F1F2F1 F2FF力的合成实
8、验一Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.我们需要研究的是： 合力F与分力F1、F2有什么关系？同学们在操作时时要注意下面几个问题: 1. 几个力的方向是沿着拉线方向的，因此要把
9、拉线的 方向描在木板的白纸上。 2. 几个力的大小由弹簧秤读出，用力的图示法在纸上 画出表示几个力的箭头。 3. 怎样表述合力的大小、方向与分力的大小、方向的 关系？ 建议用虚线把合力的箭头端分别与两个分力的箭头端 连接，也许能够得到启示。 4. 得出你的结论后，改变F1和F2的大小和方向，重做 上述实验，看看结论是否相同。Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slides for .NET 3.5 C
10、lient Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.F2F合F1O求两个力的合力时，可分别用表示这两个力的线段 为邻边作平行四边形，这两个邻边之间的对角线对角线就代表 合力的大小和方向，这叫做力的平行四边形定则平行四边形定则。3 3、结论、结论：Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with A
11、spose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011
12、Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.【例题】力F145N，方向水平向右。力F260N,方向竖直向上。 求这两个力的合力F的大小和方向。解：方法一：（作图法）取6mm长的线段表示15N的力作出力的平行四边形定则如图所示合力大小F15 N (30/6)=75N合力方向：与F1的夹角为53或与水平方向成53方法二：计算法解三角形法（直角三角形）还可作出力的示意图，利用直角三角形进 行计算求解Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 C
13、lient Profile 5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.4、多力合成的方法 ：F1F2 F3F4F12F123F1234先求出任意两个力的合力 ，再求出这个合力跟第三个力 的合力，直到把所有的力都合 成进去，最后得到的结果就是 这些力的合力逐次合成法Evaluation only.Evaluation only. Created with A
14、spose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.思考2：Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspo
15、se.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.5、合力与分力间夹角关系：0时，即F1、F2共线同方向：F合F1F2 合力方向与两个力的方向相同180时，即F1、F2共线反方向：F合F1F2 合力方向与分力F1、F2中较大 的方向相同。Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5
16、.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.1、两个力F1和F2的夹角在由0变为 180过程中，合力的大小怎样变化？你能不能确定出两个力的合力 大小范围？思 考2、合力的大小一定大于分力的大小吗？Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.Evalu
