题目内容
(10分)如图所示,一质量m=2.6kg的木块置于水平地面上,当用与水平方向成θ=370夹角的拉力F=10N拉木块时,木块做匀速直线运动。
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241606101802219.png)
(1)对木块受力分析,画出力的示意图,并建立直角坐标分解拉力F;
(2)求木块受到的支持力N和摩擦力f;
(3)如果撤去拉力F,当木块处于静止时,分别改用水平拉力F1=2N,F2=7N拉木块时,求木块受到的摩擦力大小各是多少。(g="10" m/s2,设最大静摩擦力等于滑动摩擦力)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241606101802219.png)
(1)对木块受力分析,画出力的示意图,并建立直角坐标分解拉力F;
(2)求木块受到的支持力N和摩擦力f;
(3)如果撤去拉力F,当木块处于静止时,分别改用水平拉力F1=2N,F2=7N拉木块时,求木块受到的摩擦力大小各是多少。(g="10" m/s2,设最大静摩擦力等于滑动摩擦力)
(1)(2)(3)
试题分析:(1)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241606103985126.png)
(2)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160610601688.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160610710516.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160610898529.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160611007461.png)
(3)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160611194475.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160611303526.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160611553864.png)
当F1=2N,
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160611787506.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160611990495.png)
当F2=7N,
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160612177544.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824160612364580.png)
点评:此类题型考察了对于物体的受力分析、通过正交分解法求静摩擦力的方法。
![](http://thumb2018.1010pic.com/images/loading.gif)
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