题目内容
如图所示,一物体以初速度v0冲向光滑斜面AB,并能沿斜面升高h.下列说法中正确的是( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241139208861963.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241139208861963.jpg)
A.若把斜面从C点锯断,由机械能守恒定律知,物体冲出C点后仍能升高h |
B.若把斜面弯成圆弧形,物体仍能沿AB′升高h |
C.若把斜面从C点锯断或弯成圆弧状,物体都不能升高h,因为机械能不守恒 |
D.若把斜面从C点锯断或弯成圆弧状,物体都不能升高h,但机械能仍守恒 |
D
物体到达B时速度为零,由机械能守恒定律有mgh=
mv02.若从C锯断,到达最高点时物体有水平速度,则mgh′+
mvx2=
mv02,h′<h;若把斜面弯成圆弧状,到达圆弧最高点时速度v<
,则不能到达最高点B′处,答案为D.
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824113920995225.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824113920995225.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824113920995225.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824113921276284.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
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