英语周报八年级 2018-201答案

4.D【解析】由图可知弹簧振子的振动方程为x=5sin2t,将=0.1s与t=0.2s分别代人可得弹簧的形变量之比x1:x2=1:2,回复力之比为1:2,故A项错误;t=0.1s与t=0.3s两个时刻,弹簧振子的加速度相同,速度大小相等、方向相反,故B项错误;t=0到t=0.2s的时间内,弹簧振子的动能逐渐减小,机械能逐渐减小,故C项错误;由图可知在t=0.2s与t=0.6s两个时刻弹簧的形变量相同,储存的弹性势能相同,故D项正确。

第二节书面表达范文:Dear PetIm very happy to know that you are interested in the 7th Military World Games, and feel it a greal pleasure totell you some relevant information.Wuhan,my hometown, saw the opening ceremony of the games on Oct 18. This is the first time thesehave ever been held in China. More than 9, 000 military athletes from 109 countnes came to compete in 329like shooting, swimming, basketball and so on. It is said that Wuhan Military World Games, which has the largestnumber of competitors and events, is the most successful in history. As a Wuhan native, I'm really proud that our cityand the games have made each other better.If there is anything eise that you'd like to know. please don'? hesitate to contact me. Loking forward to hearingfrem you son.YLi Hua

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