题目内容
(18分)如下图所示,让小球从图中的C位置由静止开始摆下,摆到最低点D处,摆线刚好被拉断,小球在粗糙的水平面上由D点向右做匀减速运动,到达小孔A进入半径R=0.3m的竖直放置的光滑竖直圆弧轨道,当小球进入圆轨道立即关闭A孔,小球恰好能做圆周运动。已知摆线长L=2m,
,小球质量为m=0.5kg,D点与小孔A的水平距离s=2m,g取10m/s2。求:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250006096092682.jpg)
(1)小球摆到最低点时的速度以及小球在最低点时对绳子的拉力
(2)小球运动到光滑竖直圆弧轨道最高点时的速度
(3)求粗糙水平面动摩擦因数μ。
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000609593427.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250006096092682.jpg)
(1)小球摆到最低点时的速度以及小球在最低点时对绳子的拉力
(2)小球运动到光滑竖直圆弧轨道最高点时的速度
(3)求粗糙水平面动摩擦因数μ。
(1)
(2)
(3)![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000609671557.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000609640532.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000609656687.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000609671557.png)
试题分析:(1)对CD段应用动能定理,得
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250006096871092.png)
代入数据解得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000609734545.png)
在最低点有:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000609874169.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000609890821.png)
解得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000609640532.png)
由作用力与反作用力的关系可知:小球在最低点对绳子的拉力为什10N。
(2)小球运动到光滑竖直圆弧轨道最高点时,
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000609921720.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000610077622.png)
由动能定理得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000610093991.png)
代入数据解得:小球在A点时的速度为
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000609656687.png)
(3)对DA段应用动能定理,有
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250006101391034.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000609671557.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
练习册系列答案
相关题目