题目内容
某人骑自行车以4m/s的速度匀速前进,某时刻在他正前方7m处以10m/s的速度同向行驶的汽车开始关闭发动机,然后以2m/s2的加速度匀减速前进,求此人需多长时间才能追上汽车?
8s
(1)对汽车刹车过程:![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122212894450.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122212909324.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122212925265.gif)
为停车时间(2分)
(2)设汽车在匀减速过程中被人追上
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122212940446.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122212956610.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122212987474.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122213003447.gif)
(2分)
故相遇前车已停下
(3)![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122213034462.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122213050562.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122213065547.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122213081386.gif)
即此人需8S追上汽车
(2分)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122212894450.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122212909324.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122212925265.gif)
为停车时间(2分)
(2)设汽车在匀减速过程中被人追上
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122212940446.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122212956610.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122212987474.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122213003447.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122213018416.gif)
故相遇前车已停下
(3)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122213034462.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122213050562.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122213065547.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824122213081386.gif)
即此人需8S追上汽车
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082412221309672.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
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