题目

摩擦传动是传动装置中的一个重要模型，如图所示的两个水平放置的轮盘靠摩擦力传动，其中O、O'分别为两轮盘的轴心，已知两个轮盘的半径之比r甲：r乙=3：1，且在正常工作时两轮盘不打滑.今在两轮盘上分别放置两个同种材料制成的完全相同的滑块A，B，两滑块与轮盘间的动摩擦因数相同，两滑块距离轴心O、O＇的间距的关系为RA=2RB若轮盘乙由静止开始缓慢地转动起来，且转速逐渐增加，则下列叙述正确的是（ ）A.滑块A和B在与轮盘相对静止时，线短文改错     If someone asks you how you can make you always happy, you will perhaps find rather difficult to give him a proper answer. Do you remember the old saying "No human being can really be happy which is not giving or trying  give happiness to others?" If you will always think of taking more from others and giving them less, you won't be able to have happiness in your life even you are very rich. Here is the article for you. If each of you follows it, your unhappy day will come to an end. So you should learn to give out your own interests when necessarily.