题目内容
如图所示,一台玩具电机的轴上安有一个小皮带轮甲,通过皮带带动皮带轮乙转动(皮带不打滑),皮带轮乙上离轴心O距离2mm处安有一个圆环P.一根细绳一端固定在圆环P上,另一端固定在对面的支架上,绳呈水平方向且绷直.在绳上悬挂着4个单摆a、b、c、d.已知电动机的转速是149r/min,甲、乙两皮带轮的半径之比为1:5,4个单摆的摆长分别是100cm、80cm、60cm、40cm.电动机匀速转动过程中,哪个单摆的振幅最大:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250046117016033.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250046117016033.png)
A.单摆a | B.单摆b |
C.单摆c | D.单摆d |
A
试题分析:据题意,当驱动力周期与物体固有周期相等时,振幅最大;电动机角速度为:
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/201408250046117171205.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004611748527.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004611764992.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004611779794.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140825/20140825004611795856.png)
![](http://thumb2018.1010pic.com/images/loading.gif)
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