题目内容
(16分)
如图所示,质量
的物体与地面的动摩擦因数
。物体在与地面成
的恒力F作用下,由静止开始运动,运动0.20s撤去F,又经过040s物体刚好停下。(
)求
(1)撤去F后物体运动过程中加速度的大小;
(2)撤去F时物体的速度;
(3)F的大小。![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241211022802845.jpg)
如图所示,质量
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121102217465.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121102233318.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121102248280.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121102264502.gif)
(1)撤去F后物体运动过程中加速度的大小;
(2)撤去F时物体的速度;
(3)F的大小。
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241211022802845.jpg)
(1)![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121102295450.gif)
(2)![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121102311434.gif)
(3)F=54.5N
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121102295450.gif)
(2)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121102311434.gif)
(3)F=54.5N
(1)撤去F后物体的受力情况如右图所示,根据牛顿运动定律
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241211023261015.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121102326586.gif)
又因为![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121102342398.gif)
所以
4分
(2)设撤去F时物体的速度为v,
因为![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121102389395.gif)
所以
6分
(3)物体受恒力F作用时的受力情况如右图所示,设物体在F作用过程中的加速度为
,则
=10m/s2
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241211024511219.jpg)
根据牛顿运动定律![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121102467546.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121102498606.gif)
又因为![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121102514412.gif)
所以F="54.5N " 6分
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241211023261015.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121102326586.gif)
又因为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121102342398.gif)
所以
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121102358555.gif)
(2)设撤去F时物体的速度为v,
因为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121102389395.gif)
所以
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121102311434.gif)
(3)物体受恒力F作用时的受力情况如右图所示,设物体在F作用过程中的加速度为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121102420204.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121102436234.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241211024511219.jpg)
根据牛顿运动定律
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121102467546.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121102498606.gif)
又因为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824121102514412.gif)
所以F="54.5N " 6分
![](http://thumb2018.1010pic.com/images/loading.gif)
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