题目内容
如图7-6-10所示,在一个很长的斜面上的某处A,水平抛出一个物体.已知物体抛出时的动能为1.5 J,斜面的倾角θ=30°.空气阻力不计,求它落到斜面上B点时的动能.
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241204438541765.jpg)
图7-6-10
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241204438541765.jpg)
图7-6-10
3.5 J
设物体的质量为m,初速度为v0,A、B两点的高度差为h,水平距离为s,则
h=stan30°
由平抛运动规律可得h=
gt2,s=v0t
解得h=![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120443963421.gif)
以B点所在平面为参考平面,根据机械能守恒定律得EkB=
mv02+mgh
则EkB=
mv02=
EkA=
×1.5 J="3.5" J.
h=stan30°
由平抛运动规律可得h=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120443948225.gif)
解得h=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120443963421.gif)
以B点所在平面为参考平面,根据机械能守恒定律得EkB=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120443948225.gif)
则EkB=
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120444026230.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120444041221.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120444041221.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
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