题目内容
神奇的黑洞是近代引力理论所预言的
一种特殊天体,探寻黑洞的方案之一是观测双星系统的运动规律.天文学家观测河外星系大麦哲伦云时,发现了LMCX-3双星系统,它由可见星A和不可见的暗星B构成.两星视为质点,不考虑其他天体的影响,A、B围绕两者连线上的O点做匀速圆周运动,它们之间的距离保持不变,如图4
-3-5所示.引力常量为G,由观测能够得到可见星
A的速率v和运行周期T.
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241226024483455.jpg)
(1)可见星A所受暗星B的引力可等效为位于O点处质量为m/的星体(视为质点)对它的引力,设A和B的质量分别为m1、m2,试求m/(用m1,m2表示);
(2)求暗星B的质量m2与可见星A的速率v、运行周期T和质量m1之间的关系式;
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082412260240172.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082412260241765.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082412260243265.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241226024483455.jpg)
(1)可见星A所受暗星B的引力可等效为位于O点处质量为m/的星体(视为质点)对它的引力,设A和B的质量分别为m1、m2,试求m/(用m1,m2表示);
(2)求暗星B的质量m2与可见星A的速率v、运行周期T和质量m1之间的关系式;
(1)设 A、B的圆轨道半径分别为
、
,由题意知,A、B做匀速圆周运动的角速度相同,设其为
。由牛顿运动定律,有
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122602557291.gif)
设 A、B之间的距离为
,又
,由上述各式得:
,①
由万有引力定律,有:
将①代入得:![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122602651788.gif)
令
比较可得:
-②
(2)由牛顿第二定律,有:
③
又可见星 A的轨道半径:
④
由②③④式解得:
⑤
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122602479196.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122602495199.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122602510201.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122602526477.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122602542489.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122602557291.gif)
设 A、B之间的距离为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122602573185.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122602588273.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122602604547.gif)
由万有引力定律,有:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122602635570.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122602651788.gif)
令
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122602666574.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122602682626.gif)
(2)由牛顿第二定律,有:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122602698640.gif)
又可见星 A的轨道半径:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122602713447.gif)
由②③④式解得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122602729758.gif)
略
![](http://thumb2018.1010pic.com/images/loading.gif)
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