A、v<sub>e</sub>=BD·<img width="28" height="23" src="http://admintk.100xuexi.com/UpLoadImage/2013-05-07/1c29d00c-1425-4dbb-8235-b2f3a9b6fab7.png" />，方向垂直AB
B、v<sub>e</sub>=R·<img width="16" height="15" src="http://admintk.100xuexi.com/UpLoadImage/2013-05-07/a3918461-9a71-437d-ae54-25c87b7c8590.png" />，方向平行EB
C、v<sub>e</sub>=BC·<img width="28" height="23" src="http://admintk.100xuexi.com/UpLoadImage/2013-05-07/1c29d00c-1425-4dbb-8235-b2f3a9b6fab7.png" />，方向垂直BC
D、v<sub>e</sub>=R·<img width="16" height="15" src="http://admintk.100xuexi.com/UpLoadImage/2013-05-07/a3918461-9a71-437d-ae54-25c87b7c8590.png" />，方向平行BA
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作纯滚动，带动AB杆绕B作定轴转动，D是轮与杆的接触点，如图所示。若取轮心C为动点，杆BA为动坐标系，则动点的牵连速度为（ ）。
题54图