直角刚杆AO＝2m，BO＝3m，如图4-2-15所示。已知某瞬时A点的速度vA＝6m/s，而B点的加速度与BO成θ＝60°角。则该瞬时刚杆的角加速度α为（　　）rad/s2。图4-2-15

A、3

B、<img width="24" height="19" src="http://admintk.100xuexi.com/UpLoadImage/2013-05-07/1d8f4962-53d0-47df-ba6b-37f01be8556a.png" />

C、<img width="37" height="19" src="http://admintk.100xuexi.com/UpLoadImage/2013-05-07/a3bf87c3-da46-482e-b5f5-1bd9dc4cb366.png" />

D、<img width="35" height="21" src="http://admintk.100xuexi.com/UpLoadImage/2013-05-07/1e6f9918-78ea-4993-b7dc-e088566f48c4.png" />