题目内容
质量为m的汽车,启动后在发动机功率P保持不变的条件下在水平路面上行驶,经过一段时间后将达到以速度v匀速行驶的状态,若行驶中受到的摩擦阻力大小保持不变,则在车速为
时,汽车的加速度大小为( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154757461386.png)
A.![]() | B.![]() | C.![]() | D.![]() |
A
试题分析:当汽车以恒定功率启动,当匀速运动时,阻力等于牵引力,所以
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154758209457.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154757461386.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154758428579.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824154758553465.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241547587091190.png)
点评:解决本题的关键掌握功率的公式P=Fv,当功率不变时,速度增大,牵引力减小,牵引力等于阻力时,速度最大,以后做匀速直线运动.
![](http://thumb2018.1010pic.com/images/loading.gif)
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