题目

--It ________nearly 10 hours to drive from Chongqing to Shanghai.         --That’s tiring. I would rather choose the plane.         A. spends        B. costs          C. takes          D.pays 答案：C14．如图中一质量为m的小球做圆锥摆，绳长L，绳与竖直方向成30度角，求绳拉力的大小？小球做圆周运动的半径？小球的线速度及角速度？