题目

My family often had a get-together with friends in my childhood. As I was smart, there was always someone who would come up to mention my high   41   and ask, “What are you going to do when you   42  ?” Well, it started out being a teacher or a hero.   43   it was a fireman, an artist … As I grew older my dreams of the future   44  . When I was going to college, I was asked, “What will you major in?”, another question   45   to find out what I would be when I grew up. By then I made up my mind to become a   46   programmer. So I was studying software for如图所示，一根长l=0.8m轻绳一端固定在O点，另一端栓一质量m=0.1kg的小球静止于A点，其右方有底面半径r=0.2m的转筒，转筒顶端与A等高，下部有一小孔，距顶端h=0.8m．现使细绳处于水平线上方30°的位置B点处而伸直，且与转筒的轴线、OA在同一竖直平面内，开始时小孔也在这一竖直平面内．将小球由B点静止释放，当小球经过A点时轻绳突然断掉，同时触动了光电装置，使转筒立刻以某一角速度匀速转动起来，且小球最终正好进入小孔．不计空气阻力，g取l0m/s2．试求：（1）小球到达A点时的速率？（2）转筒轴线距A点的距离L和转筒转动的角速度ω