2021-2022英语周报外研版27期答案

7.CD解析:要保证小球能通过环的最高点,小球在最高点最小速度满足mg=m,对小球从最低点运动到最高点的过程应用机械能守恒定律得m=m+2mg,可得小球在最低点瞬时速度的最小值为√5gr,A项错误、C项正确;为了不使环在竖直方向上跳起,则在最高点球有最大速度时,对环的压力为3mg,满足4mg=m,从最低点到最高点由机械能守恒定律得2m=2=mn2+2mgr,可得小球在最低点瞬时速度的最大值为2√2g,B项错误、D项正确。

书面表达One possible versionDear PeterI'm writing to invite you to see the Chinese Painting Exhibition to be held in our city.The exhibition will start at 8: 30 am on Saturday and last till 5: 00 pm on Sunday in the city museum It'ssaid that a large number of Chinese paintings, some of which are original works by famous painters like ZhangDaqian and Qi Baishi, will be on display. Besides, there will be various souvenirs to be sold. I know you re veryinterested in traditional Chinese culture, so I can t wait to tell you the news and hope we can go together.Looking forward to your reply.You

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