题目内容
倾角为30°的长斜坡上有C、O、B三点,CO =" OB" = 10m,在C点竖直地固定一长10 m的直杆AO。A端与C点间和坡底B点间各连有一光滑的钢绳,且各穿有一钢球(视为质点),将两球从A点由静止开始、同时分别沿两钢绳滑到钢绳末端,如图所示,则小球在钢绳上滑行的时间tAC和tAB分别为(取g = 10m/s2)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241600283992653.png)
A.2s和2s B.
s和 2s C.
s和4s D.4s 和
s
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241600283992653.png)
A.2s和2s B.
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160028524336.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160028524336.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160028524336.png)
A
试题分析:由几何关系可得
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160029319588.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160029491695.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241600297091028.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160029959533.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241600302401026.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160030396533.png)
故选A
点评:关键是有几何关系确定两钢球的位移、由牛顿第二定律确定加速度,由匀变速直线运动规律可求出钢球的运动时间。
![](http://thumb2018.1010pic.com/images/loading.gif)
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