题目内容
如图所示,公路上一辆汽车以v1=10m/s的速度匀速行驶汽车,行至A点时,一人为搭车从距公路30m的C处开始以v2=3m/s的速度正对公路匀速跑去,司机见状刹车,汽车做匀减速运动,结果人到达B点时,车也恰好到达B点停止。已知AB=80m,求汽车在距A多远处开始刹车?
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241147412262278.jpg)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241147412262278.jpg)
60m
人、车到达B点所用时间
设汽车匀速运动时间为t1
解得
汽车刹车处离A点![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114741288493.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114741241678.gif)
设汽车匀速运动时间为t1
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114741257636.gif)
解得
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114741272272.gif)
汽车刹车处离A点
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824114741288493.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
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