题目内容
一辆汽车做直线运动,t1s末关闭发动机,t2s末静止,其v-t图如图。图中α<β,若汽车牵引力做功为W,平均功率为P,汽车加速过程和减速过程中克服摩擦力作功分别为W1和W2、平均功率分别为P1、P2,则
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241306132612478.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241306132612478.png)
A.W= W1+ W2 | B.W1> W2 |
C.P= P1 | D.P1= P2 |
ABD
对全过程由动能定理
得
,A对。克服摩擦力作功
,由图像与横轴包围面积可得
,所以
,B对。0到t1s末由动能定理
知
,
,C错.
,同理
,
,D对。
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130613401631.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130613432545.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130613463530.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130613495427.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130613526562.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130613573877.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130613651506.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130613682401.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241306137291191.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241306137601439.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824130613775435.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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