题目内容
(10分)宇航员在一星球表面上的某高处,沿水平方向抛出一个小球,经时间t,小球落到星球表面,测出抛出点与落地点之间距离为L。若抛出时的初速增大到原来的2倍,则抛出点到落地点间的距离为
L。已知两落地点在同一水平面上,该星球的质量M,万有引力常数为G,求:
(1)该星球的半径R。
(2)该星球上的第一宇宙速度。
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001448840344.png)
(1)该星球的半径R。
(2)该星球上的第一宇宙速度。
(1)
(2)![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250014488871012.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250014488721027.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250014488871012.png)
试题分析:(1)由平抛运动规律可知:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001448903589.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001448918647.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001448950650.png)
由①②③解得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001448965709.png)
又因为
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001448996873.png)
由④⑤解得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250014488721027.png)
(2)由第一宇宙速度的定义可知:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001449028711.png)
解得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250014488871012.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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