如图所示，两个质量均为m=1kg的物块A、B套在水平粗糙的CD杆上，并用不可伸长的轻绳连接，整个装置能绕过CD中点的轴OO1转动，物块A、B与杆CD间的动摩擦因素μ=0.2，开始时绳子处于自然长度（绳子恰好伸直但无弹力），物块A到OO1轴的距离为r=0.1m，物块B到OO1轴的距离为2r，现让该装置从静止开始转动，使转速ω逐渐增大，但A、B相对于杆一直未滑动，最大静摩擦力可看做等于滑动摩擦力，g=10m/s2，试求：
（1）当转速
时，杆对B的摩擦力？
（2）轻绳中刚要产生张力时，转速
等于多少？
（3）当转速
时，杆对A的摩擦力？
（1）0.8N（2）
（3）0.4N
题目分析：（1）当转速
时，杆对B摩擦力
（2）绳中刚要产生张力时，对B有：
解得
=
（3）当转速
时，设杆对A摩擦力指向圆心，
对A有：
对B有：
联立解得：
点评：分析本题的关键是判断谁随着转速增大先达到最大静摩擦力，两物块刚好不滑动时的角速度是多少。
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| One of Jack's feet is bigger than __1__. He can't find the right shoes __2__ his feet. His mother says to him, "__3__ not go to the shoemaker? A good shoemaker can make you the right __4__ . " So Jack __5__ to the shoemaker near his home. Some time later the shoemaker make __6__ a pair of shoes. Jack looks __7__ the shoes and isn't __8__ . So he says to the shoemaker, "You __9__ a good shoemaker. I want you to make me one shoe __10__ than the other, but you make one shoe smaller than the other. " | |||
| ( ) 1. A. another ( ) 2. A. for ( ) 3. A. What ( ) 4. A. foot ( ) 5. A. going ( ) 6. A. it ( ) 7. A. for ( ) 8. A. sorry ( ) 9. A. isn't ( ) 10. A. small | B. the other B. to B. How B. feet B. goes B. he B. at B. funny B. don't B. big | C. the others C. on C. Why C. shoe C. went C. him C. like C. welcome C. are C. bigger | D. other D. of D. Where D. shoes D. walk D. his D. after D. happy D. aren't D. smaller |