2121-2022七年级新目标英语周报答案

18.C在地球的表面发射飞出太阳系的最小发射速度,叫做第三宇宙速度v=16.7km/s,选项A错误;根据重力提供向心力得G1=m解得地球上的第一宇宙速度a同理得木星上的第一宇宙速度为'=、k,故木星与地球的第一宇宙速度之比一√原,选项B错在星球表面重力与万有引力相等,G1=R:,解得M=GR同理可得木星质量M,故=题选项C正确;地球密度为p-4xRmR同理可得木星密度为=,则一,选项D错误

书面表达One possible version:NOTICEA sports meeting will be held in the playground of our school from next Thursday to FridayAs you know, the pressure of study is very heavy now, especially for those senior 3. So the purpose of the sports meeting is to letevery student get relaxed, as a result of which we students can live happily and heal thilyEveryone is welcome to take part in it. Those who perform excellently at the sports meeting will get prizes. But don' t take theresults so serously because taking part is more important than the result. Good luck to everyone!

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