2022英语周报HFW18答案

reading, with a confused look on her face. Dannis stoodup,glared at her and shouted, "You stole my wallet! "Thecrowds began to gossip. The girl turned deadly pale, loo-king so restless that words failed her. A strange silencehung in the air. Abruptly, she leaped from the seatParagraph 2The gird ran and Dannis ran after her. After a whileDannis finally grabbed her by the arm. At exactly thatmoment,a policeman approached them and asked aboutwhat happened. Dannis hastened to explain it while the girlfrowned with a shake of her head. After further enquiriesthe policeman took out a wallet and handed it to Dannisadding that someone had found it in the toilet. What a mis-take he had made! Overwhelmed by guilt, Dannis made anapology to the girl第三节One possible versionParagraph 1A seat beside her was empty, and Dannis occupied itHe felt a wave of anger swept over him, "Where is my wal-let? he yelled. The black-haired girl glanced up from her

14(1)22.0(2分)(4)m√1-c0sa=m√1-cs-m√1-cos(3分)m1cosa=m1cosB1-m2(1-cos62)(3分)【解析】(1)由题图乙可知,直径d=2.2cm+0.1×氵0mm=2.20cm=22.0mm。(4)设悬点到球心的长度为L,由动能定理可得mgL(1-cosa)=mt2,则小球A到达最低点时的速度大小v=√2gL(1-csa),同理碰后小球A的速度大小v1=√2gL(1-cos6),碰后小球归的速度大小v2=√2gL(1-cos2);若两小球碰前动量守恒,则表达式m1v=m2n-m1vh成m√2gL(1-cosa)=m2√2gL(1-cost2)m1√2gL(1-cos6)成立,故要验证两小球碰撞前、后动量是否守恒,需验证m1√1-csa=m2√1-cos6-m1√1cos6是否成立d若碰撞是弹性碰擅,则还应满足的表达式为2m1V子m十m远,即方m1(√2L(1-8a)2=2n2(√2gL(1-cosa2))2+2(√2gL(1-os))2,化简得m10sa≈氵m, cos 0,-m2(1-cos 82)

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