题目内容
如图所示,在倾角a=37°的斜面上有一块竖直放置的挡板,在挡板和斜面之间放有一个m=2kg的光滑圆球,处于平衡状态。
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241530024477048.png)
(1)试画出球体的受力图;
(2)求出球体对档板和斜面的压力。(sin37°=0.6,cos37°=0.8,重力加速度g取 10m/s2)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241530024477048.png)
(1)试画出球体的受力图;
(2)求出球体对档板和斜面的压力。(sin37°=0.6,cos37°=0.8,重力加速度g取 10m/s2)
(1)球体受力如图
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241530030242773.jpg)
(2)15N、水平向左 25N、垂直于斜面向下
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241530030242773.jpg)
(2)15N、水平向左 25N、垂直于斜面向下
试题分析:(1)球体受力如图所示球受到斜面的支持力为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824153003040352.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824153003149382.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241530030242773.jpg)
(2)小球的受力分析如图所示,由共点力的平衡条件可得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241530061608010.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824153006222757.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824153006487753.png)
根据牛顿第三定律,球对挡板的压力
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824153006643516.png)
球体对斜面的压力
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824153006784481.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824153006893169.png)
联合以上各式解得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824153007080629.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824153007657631.png)
点评:不好求解的力可用牛顿第三定律进行转换,如本题转换成对小球的力后,对小球进行受力分析,运用力的合成或分解结合共点力平衡条件解决问题。
![](http://thumb2018.1010pic.com/images/loading.gif)
练习册系列答案
相关题目