英语周报Hz九年级第21答案

One possible versionThen I wondered whether the man would still be at the same spot. I walked out the doorand back to the street where I had met him. There the man was, at the same spot, knees curledup against his chest, with the same cardboard sign shading his head. I walked down the street,and before I could think twice, I stood before him. He cautiously glanced in my direction.Ismiled and held up the lunch bag. "I brought you some lunch, "I saidI handed him the bag, and he looked closely at it. " Thank you for this. I was praying thismorning, asking for someone,s heart to open. We talked for a little while. As he shared hisstory, there was an, open, honest tone in his voice. There was something about giving thatmade me feel like I was talking with a brother. "I hope you have a nice day, "I told him<"Thank you! It's already gotten a lot better, " he said. As I walked by, his thank fulness hadbecome mind. My day, too, had already gotten a lot better. Anything helps, indeed

12.AB【解析】开始时,物块a、b及传送带均静止且物块a不受传送带摩擦力的作用,有m2gsin0=mg。物块b下降的高度为h,则物块a上升的高度为hsin0,物块a重力势能的增加量为m。g×hsin日ngh,A项正确;除重力外其他力做的功等于物体机械能的变化量,故B项正确;对物块a、b及绳子组成的系统,由前面分析知,重力势能保持不变,重力对两者做的正负功代数和为零,由动能定理知摩擦力对物块a做的功等于物块a、b动能增加量之和,C项错误;在运动过程中毎一时刻,物块a、b的速率均相等,对物块b进行分析,重力做功的瞬时功率Pn,对物块a进行分析,物块a克服重力做功的瞬时功率P。=m, gUsin9=mgv,所以重力对物块b做功的瞬时功率大小相等,D项错误。

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