题目内容
一人先向北走了40m,耗时10s,随即又向东行走了30m,耗时又是10s。
试求:(1)此人在前10s内的位移和路程
(2)在整个20s内的平均速度的大小和平均速率(sin37°=0.6;cos37°=0.8)
试求:(1)此人在前10s内的位移和路程
(2)在整个20s内的平均速度的大小和平均速率(sin37°=0.6;cos37°=0.8)
(1)
(2)2.5 m/s 北偏东37 3.5 m/s
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824201820553540.png)
试题分析:(1)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824201821146699.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824201820553540.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082420182248714000.png)
(2)根据几何知识可得:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408242018232361235.png)
所以有:
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824201824079573.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824201824749497.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824201825498814.png)
平均速度
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824201825951890.png)
平均速率
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824201826746921.png)
点评:本题要理解路程和位移的物理意义,画出示意图,求解它们的大小.位移大小等于起点到终点直线距离的大小,不会大于路程.
![](http://thumb2018.1010pic.com/images/loading.gif)
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