题目内容
(13分)如图所示,某滑冰运动员参加直线滑行练习,在滑行时,左右脚交替向后蹬冰,每次蹬冰的时间t1=1s,冰面给人水平向前的动力F=165N,左右脚交替时有t2=0.5s的时间不用蹬冰。已知整个过程中运动员受到的阻力f=55N,运动员总质量rn=55kg,设运动员由静止开始滑行,求0-3s内运动员的位移。
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/2014082500400953159612.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/2014082500400953159612.png)
6m。
试题分析:
蹬冰时的加速度
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004009547928.png)
不蹬冰的加速度
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004009562836.png)
运动员滑行时前3s内的速度图象如图所示:(3分)
0~1s内:加速
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/2014082500400957812686.png)
位移:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004009765763.png)
1s末的速度 :
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004009781696.png)
1s~1.5s内:减速
1.5s末的速度:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004009812823.png)
位移:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250040098271031.png)
1.5s~2.5s内:加速
2.5s末的速度:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004009843852.png)
位移:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004009874908.png)
2.5s~3.0s内:减速
3.0s的速度:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004009890818.png)
位移:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250040099051026.png)
3s内总位移:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004009921751.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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