题目内容
如图所示,固定的光滑竖直圆形圆形轨道,其半径为R,在它的底端静止一个质量为m小球,现给小球一个水平冲量,使小球始终不离开圆形轨道在竖直圆内运动,试求冲量应满足的条件?![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241151550851498.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241151550851498.gif)
I![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115155100140.gif)
;I![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115155116140.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115155147562.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115155100140.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115155116574.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115155116140.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115155147562.gif)
当小球运动到与竖直圆的高度为圆的半径R时速度为零,设小球的初速度为
,由机械能守恒得
…………………… (2分)
由动量定理得
解得
…………………… (2分)
当小球的动量较大时,小球刚好通过最高点的速度为
,由牛顿第二定律可得:
…………………… (2分)
再由机械能守恒列式有:
…………………… (2分)
由动量定理得![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115155256457.gif)
解得
…………………… (2分)
所以冲量I![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115155100140.gif)
;I![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115155116140.gif)
…………………… (2分)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115155147204.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115155163592.gif)
由动量定理得
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115155178450.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115155147562.gif)
当小球的动量较大时,小球刚好通过最高点的速度为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115155210185.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115155225518.gif)
再由机械能守恒列式有:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115155241742.gif)
由动量定理得
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115155256457.gif)
解得
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115155116574.gif)
所以冲量I
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115155100140.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115155116574.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115155116140.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115155147562.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
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