问题 多选题

如图所示,小球从竖直砖墙某位置静止释放,用频闪照相机在同一底片上多次曝光,得到了图中1,2,3,4,5,…所示小球运动过程中每次曝光的位置。连续两次曝光的时间间隔均为T,每块砖的厚度为 d。根据图中的信息,下列判断正确的是

[ ]

A.能判定位置“1”是小球释放的初始位置

B.能求出小球下落的加速度为

C.能求出小球在位置“3”的速度为

D.如果已知d和T的数值,就能判定小球下落过程中机械能是否守恒

答案

BCD

阅读理解

阅读理解。

     The first English dictionary was published in 1604. The dictionary was actually nothing more than a list

of about 3, 000 difficult words, each followed by a one-word definition.

     The author, Robert Cawdrey, made no attempt to include everyday words in his dictionary. No one, he

reasoned, would ever have to look up a word in a dictionary if he already knew the meaning of the word.

During the 1600's more dictionaries were published. Each followed Cawdrey's lead and presented a few

thousand hard words. Around 1700 one dictionary maker, John Kersey, did define easy words as well as hard

words. But until the 1750's all the dictionaries were rather crude and not very valuable.

     A man named Dr Samuel Johnson changed all this. In 1755 Dr Johnson produced the first modern

dictionary. He included in his dictionary all important words, both easy and hard, and he gave good meanings.

He also gave good sentences to show how each word was actually used in speech and in writing. By the end

of the 1700's most dictionary makers had followed Johnson's example. Dictionaries were getting better and

better.

      The 1800's saw the greatest improvement in the quality of dictionaries. In England scholars planned and

prepared the Oxford English Dictionary, a twenty-volume (卷;册;部) work. One of the most interesting

features of the Oxford Dictionary is its word histories. It traces (追溯;探索) the history of each word from

its earliest recorded use up to the time of the printing of the dictionary.

1. The first English dictionary _______.

A. defined easy words as well as hard ones

B. was just a list of difficult words with one-word definitions

C. included a number of everyday words

D. was considered to be a very valuable one

2. According to the passage, before 1755 all English dictionaries _______.

A. were of no value

B. only defined hard words

C. defined both easy words as well as hard words

D. were far from being perfect

3. Which of the following statements is not true about Dr Johnson's dictionary?

A. It was not very valuable.

B. It was the first modern English dictionary.

C. It included easy words as well as hard ones.

D. It gave sentences to show the usage of words.

4. The most interesting feature of the Oxford Dictionary was that ______.

A. it had a complete list of difficult words

B. it gave sentences showing how each word was actually used

C. it was a 20-volume work

D. it showed the history of each word

5. This passage is mainly about _____.

A. the difference of English dictionaries

B. the origin of English dictionaries

C. the development of English dictionaries

D. the features of English dictionaries

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