题目内容
甲、乙两人同时同地向相
同方向运动,甲以V=6m/s速度匀速运动,乙从静止以a=2m/s2的加速度做匀加速直线运动,试求:
(1)经多长时间乙追上甲?
(2)乙从开始运动后,在追上甲之前经过多长时间两人相距最远?此时两人相距距离是多少?
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082412364660485.gif)
(1)经多长时间乙追上甲?
(2)乙从开始运动后,在追上甲之前经过多长时间两人相距最远?此时两人相距距离是多少?
(1)乙追上甲时,
,设此时经历的时间为
,此时
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824123646651890.gif)
则有:
(4分)
(2)当V甲=V乙时二者相距最远,设此时经历了
的时间,
则
,有:![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082412364671472.gif)
(4分)
,![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241236467451009.gif)
此时两人相距距离为:
(2分)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824123646620278.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824123646636199.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824123646651890.gif)
则有:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824123646667503.gif)
(2)当V甲=V乙时二者相距最远,设此时经历了
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824123646682204.gif)
则
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824123646698643.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082412364671472.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824123646714527.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824123646729630.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241236467451009.gif)
此时两人相距距离为:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824123646760657.gif)
略
![](http://thumb2018.1010pic.com/images/loading.gif)
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