题目内容
如图所示,一足够长的固定斜面与水平面的夹角为37°,质点A以初速度v1从斜面顶端水平抛出,距离斜面顶端L=15m的质点B,正以速度v2沿斜面向下匀速运动,要使质点A和质点B在斜面上相遇,v1至少应大于________m/s,若v2=20m/s,则v1="________" m/s时两质点才能相遇。(sin37°=0.6,cos37°=0.8,g=10 m/s2) ![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241308149882625.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241308149882625.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130815019385.png)
要使质点A和质点B在斜面上相遇,至少落在斜面上的位置超过L,相应的竖直位移
,水平位移
,计算的
,所以v1至少应大于
,如果v2=20m/s,
(1),
(2),联立解得v1="20" m/s
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241308150501149.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130815097965.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130815144697.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130815175592.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241308152221165.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130815237883.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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