题目
题型:不详难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191201/20191201113935-70882.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191201/20191201113935-24591.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191201/20191201113935-35366.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191201/20191201113936-39889.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191201/20191201113937-82912.gif)
答案
![](http://img.shitiku.com.cn/uploads/allimg/20191201/20191201113937-16038.gif)
解析
这时起重机以O为转动而保持平衡。
![](http://img.shitiku.com.cn/uploads/allimg/20191201/20191201113937-72870.gif)
核心考点
举一反三
![](http://img.shitiku.com.cn/uploads/allimg/20191201/20191201113914-30270.gif)
(1)小物块Q的质量m2;
(2)烧断细绳后,物块P第一次到达D点时对轨道的压力大小;
(3)P物块P第一次过M点后0.3s到达K点,则MK间距多大;
(4)物块P在MN斜面上滑行的总路程.
![](http://img.shitiku.com.cn/uploads/allimg/20191201/20191201113915-83315.gif)
![](http://img.shitiku.com.cn/uploads/allimg/20191201/20191201113704-93633.gif)
如图所示,一个边长为a,质量为m的立方体ABCD静止在粗糙斜面上,斜面倾角为
![](http://img.shitiku.com.cn/uploads/allimg/20191201/20191201113704-69405.gif)
①要想用最小的力使立方体翻转,这力应怎样作用在物体上?当立方体底面(除过B点的棱)刚刚离开斜面时,这个最小力是多大?
②在翻转过程中,外力至少要对立方体做多少功?
![](http://img.shitiku.com.cn/uploads/allimg/20191201/20191201113657-71742.jpg)
![](http://img.shitiku.com.cn/uploads/allimg/20191201/20191201113657-61841.jpg)