2018-2022 英语周报 七年级 GZ 12答案

22.【答案】(1)A点(1分)(2)BC(2分)(3)m1√L1=m1√2+m2√L(2分)【解析】(1)第二次将质量为m2的物块b放在B点,为了保证第二次物块a滑到B点时的速度与第一次相同,再将物块a放在A点由静止释放(2)对圆弧面是否光滑没有要求,只要能保证物块a滑到B点有较大的速度即可,A项错误;为了保证a、b碰撞后,a能沿水平面向前滑,a的质量应该大于b的质量,B项正确;为了使a、b在水平面上滑动有相同的加速度,/25因此a、b应该由同种材料制成,C项正确;水平面不能太光滑,不然物块滑行的距离比较远,不利于测量距离,D项错误(3)设碰撞前物块a的速度大小为v0,则=/2gL2,碰擅后a的速度大小为v1=√2gL2,b的速度大小为v2=√2gL3,因此如果等式m=mm功成立,即m√D1=m1√2+m√L成立,则动量守恒定律得到验证。

第四部分:写作第一节:应用文参考范文(满分15分)Dear JohnI am writing to offer my sincere congratulations to you on your winning the award. Asyour student, I just want you to know how glad I am at your achievement.For these years, you ve shown great passion in teaching and kept on improving ourEnglish ability. It is your humorous and instructive teaching that makes English learning anentertaining and eye-opening experience for us. Without your selfless devotion, wecouldn' t have made such great progress. Thank you for your company.I really hope that you can enjoy your stay here and make mor e achievementsYoursLi Hua

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