题目内容
(10分)如图所示,长度为L的细线下挂一个质量为m的小球,小球半径忽略不计,现用一个水平力F拉小球,使悬线偏离竖直方向θ角并保持静止状态,
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250045346671777.png)
(1)求拉力F的大小;
(2)撤掉F后,小球从静止开始运动到最低点时的速度为多大?
(3)在最低点绳子拉力为多少?
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250045346671777.png)
(1)求拉力F的大小;
(2)撤掉F后,小球从静止开始运动到最低点时的速度为多大?
(3)在最低点绳子拉力为多少?
1)
2)
3) ![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004534745775.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004534698613.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004534714794.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004534745775.png)
试题分析:解:(1)小球处于静止状态,合外力为零,对其进行受力分析,如图所示,根据平衡条件得
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004534760704.png)
(2)根据机械能守恒定律:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250045347761076.png)
v=
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004534714794.png)
(3)拉力与重力的合力提供向心力:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004534823839.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004534838897.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250045348542421.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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