题目内容
如图所示,一个质量m=2 kg的滑块在倾角为θ=37°的固定斜面上,受到一个大小为40 N的水平推力F作用,以v0=10 m/s的速度沿斜面匀速上滑。(sin 37°=0.6,取g=10 m/s2)
(1)求滑块与斜面间的动摩擦因数;
(2)若滑块运动到A点时立即撤去推力F,求这以后滑块再返回A点经过的时间。![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250022446722412.jpg)
(1)求滑块与斜面间的动摩擦因数;
(2)若滑块运动到A点时立即撤去推力F,求这以后滑块再返回A点经过的时间。
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250022446722412.jpg)
(1)0.5 (2)(1+
)s
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002244688322.png)
试题分析: (1)在F的作用下,物体做匀速运动,
有Fcos 37°=mgsin 37°+μ(mgcos 37°+Fsin 37°)
解得μ=0.5
(2)撤去F后,物体往上滑时
a=gsin 37°+μgcos 37°=10m/s2
t1=
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002244704425.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002244704434.png)
往下滑时a′=gsin 37°-μgcos 37°=2 m/s2
x=
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002244735338.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002244688322.png)
t=t1+t2=(1+
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002244688322.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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