题目内容
如图所示,质量为M=2kg的光滑斜面倾角为
,斜面上用细线拴住一个质量为m=1kg的小球,系统静止时细线与斜面平行。现在给斜面一个水平向左的拉力F,使斜面沿光滑水平面运动,求:(
,
)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250018463204813.png)
(1)拉力F为多少时小球与斜面刚好无弹力?
(2)当系统加速度为
时,细线上的拉力是多大?
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001846273406.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001846288682.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001846304592.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250018463204813.png)
(1)拉力F为多少时小球与斜面刚好无弹力?
(2)当系统加速度为
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001846335696.png)
(1)40N (2)10
N
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001846351305.png)
试题分析:(1)对小球分析可知
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001846351771.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001846366835.png)
对斜面和小球整体分析可知
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001846382790.png)
F=40N 2分
(2)当a=20m/s2>
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001846398738.png)
物体离开斜面,设此时细线与水平方向夹角为α
对小球分析有
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001846413701.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001846429692.png)
代入数据得T=10
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825001846351305.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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