题目内容
质量为0.2kg的小球固定在长为0.9m的轻杆一端,杆可绕O点的水平轴在竖直平面内转动。(g=10 m/s2)求:
(1)当小球在最高点的速度多大时,球对杆的作用力为零?
(2)当小球在最高点的速度分别为6m/s和1.5m/s时,球对杆的作用力。
(1)当小球在最高点的速度多大时,球对杆的作用力为零?
(2)当小球在最高点的速度分别为6m/s和1.5m/s时,球对杆的作用力。
(1)
(2)
,方向竖直向下
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824165731529618.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824165731872549.png)
试题分析:(1)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824165732371745.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824165731529618.png)
(2)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824165732933437.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824165733385862.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824165733557354.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824165733728524.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824165734383435.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824165734680856.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824165735085385.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824165731872549.png)
点评:本题难度较小,杆对球的作用力可以是拉力、弹力或者为零,因此当杆在最高点的作用力为零时只有重力提供向心力,速度越大拉力越大,速度越小弹力越大
![](http://thumb2018.1010pic.com/images/loading.gif)
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