2022 英语周报 八年级 FJM 27答案

24.(1)设物块P与Q碰撞前的速度为v,由机械能守恒定律得mh=Dm可(1分)解得=6m/s(1分)物块P、Q碰撞,取向右为正方向,设P、Q碰后速度分别为’1、w,则m1=m1v1+m2v2(1分)2m=2m101+2m:速(1分)解得v1=4m/s,v2=10m/s(2分)(2)设物块Q与小车相对静止时,共同速度为v,系统水平方向动量守恒,则m2v=(m2+Mv(1分)解得v=2.5m/s(1分)物块Q从开始运动到与小车相对静止过程,系统能量守恒,设动摩擦因数为μ则由能量守恒定律得2m=pmg·2L+2(m+MD(2分)解得=0.25(1分)经分析可知,物块Q滑至C点与小车共速时,所求轨道BCD的半径R最小,则有2m2v=m:gR+um: gL+ 2(m2+Mu(2 45)解得R=1.25m(1分)

【语篇导读】本文是说明文。介绍了濒危动物redwolf的情况。12.A【解析】词义猜测题。根据第二段 The US Fishand Wildlife Service had been working for decades toreintroduce the species into the wild,but∴可知,情况进展不利,故选A13.D【解析】推理判断题。根据第三段 the agency isfocusing on"our commitment to get the science rightand rebuild trust with our neighbors∴·"以及 the decision made by the Fish and Wildlife Service"falls wellshort of what is needed to continue red wolf recovery"A知答案为D。14.B【解析】细节理解题。根据第四段 because peooIe are afraid to have red wolves reintroduced nearhuman communities.可知答案为B。15.C【解析】细节理解题。根据最后一段 they are shyanimals that they don t get close to humans and huntmostly at night可知答案为C。

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