2022周报九年级英语答案

18【解析】(1)由运动学公式得s=2a6解得a=6m/s2(1分)由牛顿第二定律得F=ma解得F=12N(1分)(2)滑块滑到长木板上时的速度v=at=6m/s(1分)分别对滑块和长木板由牛顿第二定律得u2 mng-ma1(1分)u2mg-A(m M)g=Maz分二者速度相等时有v1=7-a1t=a2t解得t=1s分)此过程中滑块的位移=t-2a12=3.5m(1分长木板的位移4)a12=0.5m(1分)则滑块相对长木板的位移△s=s1-52=3m距长木板右端的距离a=L-△s=1m(1分)(3)由(2)得v1=v-a1t=a2t=1m/s1分)共速后两者保持相对静止一起做匀减速运动,对整体由牛顿第二定律得uI(m Mg=(m M)a3(1分)解得a3=1m/s2(1分)由运动学公式得v=2a33解得s3=0.5m(1分)长木板滑行的总距离为=2 s3=1m(1分)

第二节One possible version:Dear RussellI,m glad to inform you that our school will hold anEnglish humorous story speech contest in the center hallthis Sunday in order to develop our sense of humor andpractice our spoken English. I' d like to invite you to takert in ItEvery participant is requested to prepare a humorousstory in English by themselves. So choose your story cau-tiously. The funnier your story is, the better it is. You areexpected to deliver your speech within five minutes. Youshould tell your story at a proper pace with a clear voiceLooking forward to your participation. I'm sure youwill be one of the winnersYoursLi Hu

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