题目内容
用水平力F拉着一物体在水平地面上做匀速运动,从某时刻起力F随时间均匀减小,物体所受的摩擦力
随时间t变化如下图中实线所示。下列说法正确的是( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241254039282101.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824125403086311.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241254039282101.png)
A.F是从![]() ![]() |
B.F是从![]() ![]() |
C.F是从![]() ![]() |
D.F是从![]() ![]() |
A
力F随时间均匀减小(与时间呈线性关系),开始减小时F跟滑动摩擦力大小相等,则F是从
时刻开始减小的,由于之后外力小于摩擦力物体做减速运动,物体依然运动,所以摩擦力不变,当物体减速到零时,将保持静止状态,则摩擦力跟外力F大小相等,
时刻物体的速度刚好变为零,
时刻物体所受外力F减为零
故应该选A
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824125403959294.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824125403975333.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824125404006330.png)
故应该选A
![](http://thumb2018.1010pic.com/images/loading.gif)
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