英语周报2022第39期答案

11.【答案】ABC【解析】设两杆与导轨的摩擦因数为,两导轨宽度为l,两杆的总电阻为R,当mg<2mg时,a杆将不会运动,对b杆和c物体:2mFA-mg=(m1 m)a,FA=BLvR随着b杆速度增大,b杆所受安培力增加,b杆加速度减小,故b杆将做加速度不断减小的加速运动,稳定时F、=2mg-pmg,加速度为零b杆做匀速直线运动A正确;由2mg<2mg,得>4,b杆匀速时,2么<,C正确71g2mg>2mg时,a杆也会运动,稳定时,对a、b、c:mg-2mg=(2m y)a',FA=F,、wt,FM当pDg=a,得FA=F=5m(1 ),结合1,m5 ) <是,故b杆做加速度不断减小fa的加速运动,稳定后以a做匀加速直线运动,b正确,d错误< p>

第四部分第二节Iwo davs before my birthday last vear. Dad came home earlv. As usual. Ihelped him carry his bags into his study: When I turned to leave. he said: "Hey. wouldyou like to help me clean my comb? It's been a while since I last cleaned"It hit methen why. as a child. helping my dad clean his comb was such a joy. That routinemeant that my dad was home early to spend the evening with Mum and I. It meantwould watch TV with us or play a few video games with me. It meant a happyloving familyI pass the clean comb back to Dad. I noticed the wrinkles next to his eyes.They are more noticeable when he smiles. but his smile is still as heartw arming asbefore. The smile of a father who just wants a good life for his family. Dad carefullyplaces his comb on top of his wallet. After so many years. he still organises hispersonal items in the same careful way. I guess some things never change. And forthat. I'm glad

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