题目内容
倾角为30°的长斜坡上有C、O、B三点,CO=OB=10m,在O点竖直的固定一长10m的直杆AO。A端与C点、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,如右图所示,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/20140824/201408241301053471847.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241301053471847.jpg)
A.2s和2s |
B.![]() |
C.![]() |
D.4s和![]() |
A
设CO为l,则BO=AO=CO=l,小球在钢绳AC上滑行,加速度aAC=gsin30°,位移SAC=l,由
,则tAC=2s;小球在钢绳AB上滑行,加速度aAB=gsin60°,位移SAB=
l,由
,则tAB=2s。
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130105457640.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130105472313.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130105488637.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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