题目内容
一辆质量为4 t的汽车驶过半径为50 m的凸形桥面时,始终保持5 m/s的速率.汽车所受的阻力为车与桥面压力的0.05倍.通过桥的最高点时汽车牵引力是多少?(g="10" m/s2)
F=1.9×103 N
汽车沿凸形桥行驶到最高点时受力如图,要使汽车匀速率通过桥顶,则应有:
G-FN=m
① ( 3分)
F=Ff=kFN ② (3分)
联立①、②式求解得牵引力F=k(G-m
),代入数值得:F=1.9×103 N (1分)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241158056951527.gif)
G-FN=m
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115805632241.gif)
F=Ff=kFN ② (3分)
联立①、②式求解得牵引力F=k(G-m
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824115805632241.gif)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241158056951527.gif)
![](http://thumb2018.1010pic.com/images/loading.gif)
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