题目内容
如图所示,质量m=1kg的物体沿倾角θ=37°的固定粗糙斜面(足够长)由静止开始向下运动,已知物体与斜面间的动摩擦因素为0.25,经过1s 后物体受到水平向右的大小为F=5N的持续风力作用。求:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241548587221497.png)
(1)物理开始向下运动时的加速度;
(2)受到风力作用时物体沿斜面向下运动时的加速度。
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241548587221497.png)
(1)物理开始向下运动时的加速度;
(2)受到风力作用时物体沿斜面向下运动时的加速度。
(1)
(2)![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154858987768.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154858847653.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154858987768.png)
试题分析:(1)开始运动时物体受力如图所示,
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241548590653986.png)
并将重力正交分解
沿x 轴方向有
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154859174943.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154859252596.png)
沿y轴方向有
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154859439909.png)
由上可得
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154858847653.png)
(2)当物体受到风力作用时受力如图所示,
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241548597204069.png)
将力正交分解
沿x 轴方向有
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241548598291156.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154859985619.png)
沿y轴方向有
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241549001411080.png)
由上可得
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154858987768.png)
点评:难度较小,处理受力问题有很多种方法:合成法、分解法、正交分解、矢量三角形、相似三角形,在受到4个及以上的力的时候,通常采用正交分解法
![](http://thumb2018.1010pic.com/images/loading.gif)
练习册系列答案
相关题目