题目内容
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241203071653173.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120307243204.gif)
(1)求金属环运动的最大加速度的大小;
(2)求金属环运动的最大速度的大小.
(1)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120307259647.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120307259790.gif)
(1)开始时金属环速度为零,所受的摩擦力为最小,此时金属环所受的合外力最大,根据牛顿第二定律得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120307306588.gif)
解得金属环的最大加速度:![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120307259647.gif)
(2)当摩擦力
时,金属环所受的合外力为零,金属环达到最大速度
,则此时所受的洛伦兹力为
,方向垂直纸面向外.
因此,杆对金属环的弹力为:![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120307368775.gif)
当金属环达到最大速度时有:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120307384820.gif)
解得:![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120307337328.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120307462800.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120307306588.gif)
解得金属环的最大加速度:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120307259647.gif)
(2)当摩擦力
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120307337393.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120307337328.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120307352490.gif)
因此,杆对金属环的弹力为:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120307368775.gif)
当金属环达到最大速度时有:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120307384820.gif)
解得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120307337328.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824120307462800.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
练习册系列答案
相关题目