题目

绳子的一端拴一个重物，用手握住另一端，使重物在光滑的水平面内做匀速圆周运动，下列判断正确的是（ ）A. 半径相同时，角速度越小绳越易断B. 周期相同时，半径越大绳越易断C. 线速度相等时，周期越大绳越易断D. 角速度相等时，线速度越小绳越易断 答案：【答案】B【解析】A、重物在光滑的水平面内做匀速圆周运动，绳的拉力作为物体需要的向心力，由Fn=mrω2可得，角速度越小需要的向心力越小，绳越不容易断，所以A错误．B、由可得，周期相同时，半径越大，物体需要的向心力越大，绳越易断，所以B正确．C、由可得，线速度相等时，周期越大，物体 词汇考查. 1．The car is small，e          if you have children． 2．The accident caused the t          problem in Heping Road this morning． 3．The girl is afraid of dark．So please don't leave her a          at night． 4．You've made lots of mistakes in your homework．Please do it c          in future． 5．All the volunteers（志愿者）are working hard to i         their spoken English，because the Beijing Olympics is coming． 6．It's a difficult          （决定）for any doctor． 7．We've got lot of          （知识）of environment． 8．The Beijing Olympic Torch（火炬）is made in the shape of the paper scroll and the         clouds（祥云）graphic． 9．One day, you will realize the          （重要性）of time． 10．I can't be a nurse，for I have no          （耐心）.