题目内容
如图所示,质量分别为2m和m的A、B两物体用不可伸长的轻绳绕过轻质定滑轮相连,开始两物体处于同一高度,绳处于绷紧状态,轻绳足够长,不计一切摩擦。现将两物体由静止释放,在A落地之前的运动中,下列说法中正确的是
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250010247162013.jpg)
A.A物体的机械能增大
B.A、B组成系统的重力势能增大
C.下落t秒过程中,A的机械能减少了![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001024732727.png)
D.下落t秒时,B所受拉力的瞬时功率为![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001024763661.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250010247162013.jpg)
A.A物体的机械能增大
B.A、B组成系统的重力势能增大
C.下落t秒过程中,A的机械能减少了
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001024732727.png)
D.下落t秒时,B所受拉力的瞬时功率为
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001024763661.png)
C
试题分析:在A下降的过程中,A的机械能减小,B的机械能增大,A、B系统的机械能守恒,所以A、B选项错误;释放后,AB物体都做初速度为0,加速度为
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001024779422.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001024841550.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001024857577.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001024919717.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001024950488.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001024966685.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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