题目内容
(12分)如图所示,传送带与水平面之间的夹角为30°,其上A、B两点的距离为
=5m,传送带在电动机的带动
下以
=1m/s的速度向上匀速运动,现将一质量为
=10kg的小物体轻放在传送带上A点,已知小物体与传送带间的动摩擦因数为μ=![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082412222022685.gif)
/2,在传送带将物体从A点送到B点的过程中,g取10m/s2。求:![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082412222027265.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241222202889624.jpg)
(1)传送带对物体做的功;
(2)电动机做的功。
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122220163185.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082412222017972.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122220210185.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122220226204.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082412222022685.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122220257208.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082412222027265.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241222202889624.jpg)
(1)传送带对物体做的功;
(2)电动机做的功。
(1)255J
(2)270J
(2)270J
(1)由
得:
(2分)
当物块速度为1m/s时,位移为
="0.2m " (1分)
由功能关系得:
="255J " (2分)
(2)物块和传送带之间的相对位移
(1分)
又
="0.4s "
(1分)
得
="0.2m " (1分)
产生的热量
="15J " (2分)
电动机做的功等于物块增加的机械能与因摩擦产生的热量之和,所以
="270J " (2分)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122220304750.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122220319316.gif)
当物块速度为1m/s时,位移为
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122220335413.gif)
由功能关系得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122220366528.gif)
(2)物块和传送带之间的相对位移
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122220382433.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082412222039765.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082412222041365.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122220428370.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082412222044472.gif)
得
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122220460189.gif)
产生的热量
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122220475586.gif)
电动机做的功等于物块增加的机械能与因摩擦产生的热量之和,所以
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122220506499.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
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