题目内容
如图所示,小球被轻质细绳系住斜吊着放在静止的光滑斜面上,设小球质量
,斜面倾角
,悬线与竖直方向夹角
,光滑斜面的质量为
,置于粗糙水平面上。重力加速度为
.求:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250008223503385.jpg)
(1)当斜面体静止时,悬线对小球拉力大小;
(2)地面对斜面的摩擦力的大小和方向。
(3)若地面对斜面体的最大静摩擦力等于地面对斜面体支持力的K倍,为了使整个系统始终处于静止状态,K必须满足什么条件?
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000822162337.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000822178488.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000822178480.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000822318579.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000822334273.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250008223503385.jpg)
(1)当斜面体静止时,悬线对小球拉力大小;
(2)地面对斜面的摩擦力的大小和方向。
(3)若地面对斜面体的最大静摩擦力等于地面对斜面体支持力的K倍,为了使整个系统始终处于静止状态,K必须满足什么条件?
(1)
(2)
,水平向左 (3)![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000822396647.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000822365630.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000822381663.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000822396647.png)
试题分析:(1)设支持力为
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000822412302.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000822412304.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250008224281172.png)
可得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000822443822.png)
(2)以小球和斜面整体为研究对象,受力分析,由于系统静止,则:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250008224591071.png)
对小球和斜面整体受力分析,由平衡条件:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250008224741267.png)
所以:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000822490737.png)
又由题意可知:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000822506763.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000822521990.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825000822537642.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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