题目内容
.一辆汽车在十字路口等候绿灯,当绿灯亮时汽车开始匀加速行驶,汽车的牵引力保持为车重的0.6倍,汽车行驶时所受阻力为车重的0.3倍,恰在这时一辆自行车以6m/s的速度匀速从后面超过汽车,则:
(1)汽车从路口启动后,在追上自行车之前经多长时间两车相距最远,距离多少?
(2)若该路段汽车最大速度不允许超过9m/s,则汽车开始运动后经多长时间追上自行车?
(1)汽车从路口启动后,在追上自行车之前经多长时间两车相距最远,距离多少?
(2)若该路段汽车最大速度不允许超过9m/s,则汽车开始运动后经多长时间追上自行车?
(1)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241319405311455.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824131940562726.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241319406401052.png)
解得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824131940843414.png)
(2)当汽车速度达到10m/s时,
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241319408581194.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824131940905623.png)
此时间内自行车位移
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241319409681329.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824131940999374.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241319410301088.png)
因此
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824131941186769.png)
略
![](http://thumb2018.1010pic.com/images/loading.gif)
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