2020—2022语周报答案

第四部分写作第一节Dear Jack,Welcome to our school to study as an exchange studentAs for how to borrow books from the school libraryyou need to have your student ID card and present it to thelibrarian, who can register for you. Then you can go to thebookshelves to look for what you need. You can borrow 2books once and keep them for a week in order that you canhave enough time to finish reading them. If you haventread the book through, you can renew it. You' ll have topay for it if you get the book damaged or lost.hope all this can be of help to you. For morenformation, don,t hesitate to ask meLi Hua

第(1)问4分;第(2)问7分;第(3)问7分(1)小球释放瞬间,对整体有(m1-m2)B=(m1+m2)x1-m2)g解得分(2)小球到达最低点B时,、2速度大小分别为n、吃,如图所示,由运动的合成与分解得(2分对m、跎组成的系统,由机械能守恒定律得逍吕跑吕分有R(1分对m由机械能守恒定律得:mv=mh1分代入可解得h1=0(1分3)由于加了磁场,金属小球产生电磁感应现象,最终在磁场区域内做往返运动,到达磁场边界时v=0,此时比最低点B高h1,由几何关系可解得h1=0.4R(2分则有分)F-mg=mR,(2分)可解得F=7.硎N,则球对碗底压力为7.2牛(1分

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