七年级新目标2022－2022英语周报答案

书面表达Dear Sir or MadamI am Li Hus, an exchenge student from China. Wanting to get a library card in your library.(背景2分)1 am writing to ask for some relvant information.(目的3分)to begin with, could you please tell me what kind of books can beborrowed?(要点一6分) besides, I would be very interested to ksomething about borrowing system, including how long I can keep thebooks, how many books I can borrow once, and how much I should pay(要点二6分)L8 t but not least, I also wonder when and where I canmake it.(要点三6分)a中aThanks for your ime and I would appreciate it if you can give an earlreply.(表感谢+期回复2分)1量里的0+Yoour sincere.yLi H点国惊口人国文

17.(1)1.8m(2)0.6s(3)5J【解析】(1)物块A落到B上时(1分)SIn解得v,=2m/s(1分)物块A落到木板前做平抛运动竖直方向2g(H-h)(1分解得H=1.8m(1分(2)由木板恰好静止在斜面上,得到斜面与木板间的动摩擦因数μ0应满足mg sin 30=po mg cos 30(1分解得μo=3(1分)物块A在木板上滑行时.以A为研究对象有Mgcos30°- Mg sinA2.5 m/s分以木板B为研究对象有Mg cos30°+ mosin30-p0(M+m)gcos30°7.5m/s2(1分假设A与木板达到共同速度v共时,A还没有压缩弹簧且木板还没有到达底端则有v共=aBt1=v-aAt(1分解得v#=3m/s,t1=0.4s此过程xAv+共t1=1.41分2xu=2·t=0.6m

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