图示绳子的一端绕在滑轮上，另一端与置于水平面上的物块B相连，若物块B的运动方程为，其中ｋ为常数，轮子半径为Ｒ。则轮缘上A点的加速度大小为（　　）。题53图

A、<img width="21" height="19" src="http://admintk.100xuexi.com/UpLoadImage/2016-10-26/2538ce39-cf15-4af7-96e6-17308e24cbeb.png" />

B、<img width="53" height="48" src="http://admintk.100xuexi.com/UpLoadImage/2016-10-26/c44d1198-f054-40d0-9ab5-9961bcfa8c1f.png" />

C、<img width="73" height="44" src="http://admintk.100xuexi.com/UpLoadImage/2016-10-26/fe71e992-fe26-430d-9f1b-33461400ea79.png" />

D、<img width="97" height="48" src="http://admintk.100xuexi.com/UpLoadImage/2016-10-26/65871f77-3a99-4a6b-a12c-d675e0da4a81.png" />