题目内容
如图所示,遥控电动赛车(可视为质点)从A点由静止出发,经过时间t后关闭电动机,赛车继续前进至B点后水平飞出,恰好在C点沿着切线方向进入固定在竖直平面内的圆形光滑轨道,通过轨道最高点D后回到水平地面EF上,E点为圆形轨道的最低点。已知赛车在水平轨道AB部分运动时受到恒定阻力
0.4N,赛车的质量
0.4kg,通电后赛车的电动机以额定功率P=2W工作,轨道AB的长度L=2m,B、C两点的高度差
0.45m,连线
和竖直方向的夹角
,圆形轨道的半径R=0.5m,空气阻力忽略不计,取重力加速度
,
,
。求:
(1)赛车运动到C点时速度
的大小;
(2)赛车经过最高点D处时受到轨道对它压力ND的大小;
(3)赛车电动机工作的时间
。![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241245024049359.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824124501609219.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824124501749220.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824124501749217.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824124501765245.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824124502108285.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824124502124475.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824124502139492.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824124502217493.gif)
(1)赛车运动到C点时速度
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824124502358206.gif)
(2)赛车经过最高点D处时受到轨道对它压力ND的大小;
(3)赛车电动机工作的时间
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824124502358185.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241245024049359.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082412450249850550.jpg)
略
![](http://thumb2018.1010pic.com/images/loading.gif)
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