七年级上册英语周报答案2022-2022

参考范文Then, clutching (5mff)the tin can, he headed for the shop. " Ihave the money. " he seriously told the owner. The man went to thewindow and fetched Reubens treasure, He wiped the dust of it andgently wrapped it in brown paper. Then he placed the parcel inReuhen's hands Racing home, Reuben burst through the front door.His mother was cleaning the kitchen stove. "Here, Mom! HereReuben exclaimed as he ran to her side. He placed a small box in herwork-roughened haHis mother unwrapped it carefully, to save the paper. A bluepaper box appeared, and she lifted the lid. In gold lettering on a pair ofred, lambskin gloves was the word Mother. And a card says,"It isMothers Day. We appreciate all the things that Mom does for usThank you! "His mother had never received such a gift; she had nogift except her wedding ring. Spccchlcss, she smiled sweetly andgathered her son into her arms, with tears running down her cheeks.Long live with this happy moment!

17.答案:(1)2m/s(2解析:(1)物体1下滑过程中,对于物体1与滑块组成的系统由机城能守恒和水平方向动量中恒可得:m1gR=m1可十方m可0m,D,-m,D解得:1=2m/s(2)因瑾前物体2所受合外力为0,故碰前物体2一直保持静止,故v=0由动量守恒有:mD1=(m三个物体共速时,弹簧弹性势能最大,由动量守恒和能量守恒可知(m1+m:),(mITtm2)m)m,可+m2+m,)4+解得:E=1.51

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