题目内容
如图所示,固定在竖直面内的圆周轨道的内侧表面是光滑的,轨道半径是R,在轨道最低点A处静止看一个质量为m的小滑块(可视为质点),现用力向右推此滑块到B点(∠AOB=45°)放手,此后小滑块通过轨道最高点时对轨道的压力刚好减小到零,则推力将滑块由A到推至B所做的功是______。![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408242017026782669.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408242017026782669.jpg)
2.5mgR
试题分析:小滑块通过轨道最高点时对轨道的压力刚好减小到零,此时,
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824201702990697.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824201703676440.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824201704409521.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408242017050961220.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824201705704514.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408242017063591246.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824201706952758.png)
点评:理解应用好小滑块通过轨道最高点时对轨道的压力刚好减小到零,这一隐含条件。
![](http://thumb2018.1010pic.com/images/loading.gif)
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