题目内容
(10分)如图所示,一倾角为θ=37o的绝缘斜面高度为h=3m,底端有一固定挡板,整个斜面置于水平向右匀强电场中,场强E=1×106N/C.现有一质量为m=0.2kg,电荷量为q=-1×10-6C的小物体,沿斜面顶端从静止开始下滑,小物体与斜面间的动摩擦因数为µ=0.2,且小物体与挡板碰撞时不损失机械能(g=10m/s2,sin37o=0.6,cos37o=0.8)求:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241500225622294.png)
(1)小物体第一次与挡板碰撞前瞬间的动能;
(2)小物体从静止开始下滑到最后停止运动通过的总路程s.
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241500225622294.png)
(1)小物体第一次与挡板碰撞前瞬间的动能;
(2)小物体从静止开始下滑到最后停止运动通过的总路程s.
(1)
(2) ![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824150022749521.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824150022687548.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824150022749521.png)
试题分析:对物块进行受力分析,如图所示
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241500228111638.png)
解:(1)在运动过程中重力、静电力、摩擦力做功,
根据动能定理得
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241500230771116.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824150023139656.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241500232171066.png)
联立代入数据得
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824150022687548.png)
(2)整个过程中重力、静电力、摩擦力做功,
根据动能定理得
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241500234511045.png)
代入数据得
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824150022749521.png)
点评:本题难度中等,由问题可知本题考查的应该是功能关系的应用,此种类型题的分析,要先分析受力情况,再分析运动和做功情况,其中需要注意重力、电场力做功只与初末位置有关,而摩擦力做功与路径、路程有关
![](http://thumb2018.1010pic.com/images/loading.gif)
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