题目内容
如图所示,把小车放在光滑的水平桌面上,用轻绳跨过定滑轮使之与盛有沙子的小桶相连,已知小车的质量为M,小桶与沙子的总质量为
,把小车从静止状态释放后,在小桶下落竖直高度为
的过程中,若不计滑轮及空气的阻力,下列说法中正确的是
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241253013563201.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824125301154204.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824125301185200.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241253013563201.jpg)
A.绳拉车的力始终为![]() |
B.当M远远大于![]() ![]() |
C.小车获得的动能为![]() |
D.小车获得的动能为![]() |
BD
首先不是A,否则
匀速运动,也不是C,减少的重力势能
变为
和M的增加的动能
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824125301154204.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824125301466375.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824125301154204.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
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