题干

如图所示,套在绳索上的小圆环P下面挂一个重为G的物体Q并使它们处于静止状态.现释放圆环P,让其沿与水平面成θ角的绳索无摩擦的下滑,在圆环P下滑过程中绳索处于绷紧状态(可认为是一直线),若圆环和物体下滑时不振动,则下列说法正确的是(   )

A:Q的加速度一定小于 gsinθ

B:悬线所受拉力为 Gsinθ

C:悬线所受拉力为Gcosθ

D:悬线一定与绳索垂直

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C,D

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    If you want to learn English well, enlarging your vocabulary is important. Here are some helpful ways to help you to have a larger vocabulary.

    ____A good dictionary should be up-to-date and easy to understand. Make sure the definitions (定义) are written in clear English. I strongly recommend Longman Dictionary of Contemporary English as there is good coverage of spoken and written English, British and American English, as well as clear example sentences.

    Make notes of new words. But before you write them down on you notebook, you should look them up in the dictionary and make sure you are aware of any grammatical information.____When you write down the new word in your notebook, try to include an example sentence in English.

    Organize your notes into themes. Some people find it very helpful to do so. ____For example, you can have one page containing words which have something to do with houses, while another page containing words relating to jobs, and so on.

    ____The next time you have spare time, skip through your notebook. Choose a page where you have already stored a number of words and expressions, cover the page and try to remember what you wrote. Then look at the page and see how many words you have remembered.

    When you find a new word, check to see if you can use it in other ways. English is a flexible language—nouns, verbs and adjectives often share the same root. ____

A. Review the words in your notebook.

B. Have good English dictionaries.

C. Read books that contain some new words.

D. Look up new words and phrases in your dictionary.

E. For example, love, lovely, beloved and loveless all share one root.

F. For example, if you are looking up a verb, check to see if it can be used in a passive form.

G. So rather than have a list of words without any obvious connection, you can divide your notes into themes.