问题 多选题

如图所示,为A、B两质点做匀速圆周运动的向心加速度随半径变化的图象,其中A为双曲线的一个分支,由图可知(  )

A.A物体运动的线速度大小不变

B.A物体运动的角速度大小不变

C.B物体运动的角速度大小不变

D.B物体运动的线速度大小不变

答案

由于A为双曲线的一个分支,说明a与r成反比,由向心加速度的公式a=

V2
r
可知,A物体运动的线速度大小不变,所以A正确,B错误.

由于B的图象为直线,说明a与r成正比,由向心加速度的公式a=rω2 可知,B物体运动的角速度不变,所以C正确,D错误.

故选AC.

解答题
写作题

写作

阅读下面的短文,然后按照要求写一篇150词左右的英语短文.

    Teenagers' secrets should be kept to themselves and no one else,their parents included,has the right to

stick their nose into their private life.

    As we know,teenagers are going through a special period of development both physically and

psychologically.They are curious about and puzzled by the unexpected changes in their body and mind.

What's more,exposed to a world of adults,it is only too natural for them to begin imitating adults' behaviors in secret.Boys begin to smoke and girls begin to spend time doing their hair and care more about what to wear.Some even begin to date with a girlfriend or boyfriend without letting their parents know.They are

doing all this in secret because they are still unsure whether it is right to do so and afraid that,if found out by their parent,they will get misunderstood and even punished.In fact,in many cases,parents can not deal with such matters well but hurt their children's feelings badly,making children unwilling to communicate with them any more.When this happens,it hurts terribly feelings of the family as well.Therefore,it sounds reasonable and acceptable that teenagers should keep their secrets to themselves instead of sharing them with their

parents,who should give them the freedom in dealing with secrets.

【写作内容】

     1. 以约30个词概括上面文章的要点;

     2. 然后以约120个词就"青少年的秘密该不该与父母分享"这一话题发表你的看法,至少包含以下内容:

     (1)你是支持还是反对与父母分享秘密?

     (2)你支持或反对的理由是什么?

     (3)结合你的实际,谈谈你是具体怎么做的?

【写作要求】

      1. 在作文中可以使用自己亲身的经历或虚构的故事,也可以参照阅读材料的内容,但不得直接引用原文中的句子;

      2. 作文中不能出现真实姓名和学校名称.

      3. 题目自拟.

【评分标准】

     概括准确,语言规范,内容合适,篇章连贯.

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