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1、万有引力理论的成就,Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.,知识回顾,1:万有引力定律的内容是什么,自然界中任何两个物体都是相互吸引的,引力的大小跟物体质量的乘积成正比,跟它们的距离的二次方成反比。,2:万有引力定律的适用条件是什么,公式适用于两质点之间,“r”是指两质点中心之间的距离; 当质点是 两均质球体时,r是指两球体球心之间的距离。,Evaluation only. Created with A
2、spose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.,一、“称量地球的质量”,当时已知: 地球的半径R、地球表面重力加速度g以及卡文迪许自己已测出的引力常量G. 那么卡文迪许该如何“称量地球的质量”呢?,Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.,一、“称量地球的质量”,Evaluation
3、 only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.,科学真是迷人。根据零星的事实,增加一点猜想,竟能赢得那么多的收获! 马克吐温,Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.,一、“称量地球的质量”,不考虑地球自转的影响,Evaluation onl
4、y. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.,Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.,一、“称量地球的质量”,R-为地体的半径,g-地体表面的重力加速度,Evaluation only. Created with Aspose.Slides fo
5、r .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.,一宇航员为了估测一星球的质量,他在该星球的表面做自由落体实验:让小球在离地面h高处自由下落,他测出经时间t小球落地,又已知该星球的半径为R,试估算该星球的质量。,2hR2/Gt2,练习:,Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.,二、计算太阳的质量,我们可以测出太阳
6、某行星的公转周期T、轨道半径r, 能不能由此求出太阳的质量M?,分析: 1.将行星的运动看成是匀速圆周运动.,2.万有引力充当向心力 F引=Fn.,Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.,二、计算太阳的质量,我们可以测出太阳某行星的公转周期T、轨道半径r, 能不能由此求出太阳的质量M?,F引=Fn,只可求出中心天体的质量, 求不出环绕体的质量。,Evaluation only. Created with
7、 Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.,二、计算中心天体的质量,已知 地球半径: R = 6400103m 月亮周期: T = 27.3天2.36106s 月亮轨道半径: r 60R, 求 地球的质量M?,F引=Fn,Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.,二、计算中心
8、天体的质量,如果不知道环绕体的公转周期,而知道环绕体的线速度或角速度及其轨道半径,能不能求出中心天体的质量?,F引=Fn,Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.,登月密封舱在离月球表面h处的空中沿圆形轨道运行,周期是T,已知月球的半径是R,万有引力常数是G,据此试计算月球的质量。,练习,Evaluation only. Created with Aspose.Slides for .NET 3.5 Cl
9、ient Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.,三、计算天体的密度,已知太阳某行星的公转周期T、轨道半径r,太阳的半径R,求太阳的密度?,F引=Fn,Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.,三、计算天体的密度,已知太阳某行星的公转周期T、轨道半径r,太阳的半径R,求太阳的密度?,F引=Fn,Evaluation only. Create
10、d with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.,三、计算天体的密度,已知地球的一颗人造卫星的公转周期T、轨道半径r,地球的半径R,求地球的密度?,此卫星是一近地卫星,地球的密度又是多少呢?,Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.,四、发现未知天体,背景: 1781年
11、由英国物理学家威廉赫歇尔发现了天王星,但人们观测到的天王星的运行轨迹与万有引力定律推测的结果有一些误差,Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.,四、发现未知天体,Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.,四、发现未
12、知天体,背景: 1781年由英国物理学家威廉赫歇尔发现了天王星,但人们观测到的天王星的运行轨迹与万有引力定律推测的结果有一些误差,1:1845年英国人亚当斯和法国天文学家勒威耶据各自独立用万有引力定律计算发现了“海王星”(第8个行星)。 2:1930年3月14日人们发现了从被称为太阳系第9个行星 冥王星,Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.,小结:基本思路,2.将行星(或卫星)的运动看成 是匀速圆周运
13、动.,3.万有引力充当向心力 F引=F向.,1. 在星体表面附近 F引=G重,Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.,中心天体M,转动天体m,明确各个物理量,天体半经R,Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.,练
14、习:,1:利用下列哪组数据可以举算出地球的质量 ( ) A:已知地球的半径r和地球表面的重力加速度g B:已知卫星围绕地球运动的轨道半径r和周期T C:已知卫星围绕地球运动的轨道半径r和周期T D:已知卫星围绕地球运动的线速度V和周期T,ABCD,Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.,Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.,