题目内容
冰壶比赛是在水平冰面上进行的体育项目,比赛场地示意图如图所示.比赛时,运动员从起滑架处推着冰壶出发,在投掷线AB处放手让冰壶以一定的速度滑出,使冰壶的停止位置尽量靠近圆心O.为使冰壶滑行得更远,运动员可以用毛刷擦冰壶运行前方的冰面,使冰壶与冰面间的动摩擦因数减小.设冰壶与冰面间的动摩擦因数为μ1=0.008,用毛刷擦冰面后动摩擦因数减小至μ2=0.004.在某次比赛中,运动员使冰壶C在投掷线中点处以2 m/s的速度沿虚线滑出.求:为使冰壶C能够沿虚线恰好到达圆心O点,运动员用毛刷擦冰面的长度应为多少?(g取10m/s2)![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082419315810114283.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/2014082419315810114283.png)
S=10m
试题分析:设运动员用毛刷檫冰面得长度为S2摩擦力为f2;
则未刷的为S1所受摩擦为f1由动能定理有:
f
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824193158678195.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824193158678195.png)
f
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824193159817240.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824193159817240.png)
S1+S2=S③
-f
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824193158678195.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824193159817240.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824193201907337.png)
由①-④解得:S=10m
点评:本题考查了对动能定理的理解和运用。通过动能定理计算物体动能变化量,要知道对应的是外力对物体做的总功。
![](http://thumb2018.1010pic.com/images/loading.gif)
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