题目内容
如图所示,重10N的滑块在倾角为30o的斜面上,从
点由静止下滑,到b点接触到一个轻弹簧,滑块压缩弹簧到c点开始弹回,返回b点离开弹簧,最后又回到
点,已知,ab=1m,bc="0.2" m,那么在整个过程中以下说法错误的是
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241902077012015.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824190207031192.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824190207031192.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241902077012015.jpg)
A.滑块动能的最大值是6J |
B.弹簧的弹性势能的最大值是6J |
C.从c到b弹簧的弹力对滑块做的功是6J |
D.整个过程物体和弹簧组成的系统机械能守恒 |
A
试题分析:当滑块的合力为0时,滑块速度最大,设滑块在d点合力为0,d点在b和c之间.
滑块从a到d,运用动能定理得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824190207779363.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824190208060385.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824190208341272.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824190208606322.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824190208887277.png)
让选错误的,故选A.
点评:本题的关键是认真分析物理过程,把复杂的物理过程分成几个小过程并且找到每个过程遵守的物理规律,列出相应的物理方程解题.同时要明确弹簧弹力做的功等于弹性势能的变化.
![](http://thumb2018.1010pic.com/images/loading.gif)
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