题目内容
(12分)如图甲所示,质量为m=1kg的物体置于倾角为θ=37°的固定斜面上(斜面足够长),对物体施加平行于斜面向上的恒力F,作用时间t1=1s时撤去拉力,物体运动的部分v-t图像如图乙所示,取g=10m/s2, sin37°=0.6,cos37°=0.8,试求:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250029064214446.jpg)
(1)物体与斜面间的动摩擦因数和拉力F的大小;
(2)t=6s时物体的速度,并在图乙上将6s内物体运动的v-t图像补画完整,要求标明有关数据。
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250029064214446.jpg)
(1)物体与斜面间的动摩擦因数和拉力F的大小;
(2)t=6s时物体的速度,并在图乙上将6s内物体运动的v-t图像补画完整,要求标明有关数据。
(1)
(2)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250029064673710.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002906436753.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250029064673710.jpg)
试题分析:(1)设撤去拉力前物体的加速度大小为a1,撤去拉力后物体沿斜面继续上滑的加速度大小为
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002906483371.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002906499959.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250029065141003.png)
对物体在撤去拉力前,由牛顿第二定律得
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250029065451113.png)
对物体在撤去拉力后上滑时,由牛顿第二定律得
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250029065611128.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002906436753.png)
(2)加速上滑的时间
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002906592416.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002906623571.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002906639327.png)
由
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002906655559.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002906670480.png)
在最高点时,因
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002906701972.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002906717375.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250029067331059.png)
解得
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002906748669.png)
再经过3s物体的速度大小为
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825002906764465.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250029067793710.jpg)
![](http://thumb2018.1010pic.com/images/loading.gif)
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