木块a和b用一根轻弹簧连接起来,放在光滑水平面上,a紧靠在墙壁上,在b上施加向左

题型:不定项选择

问题:

木块a和b用一根轻弹簧连接起来,放在光滑水平面上,a紧靠在墙壁上,在b上施加向左的水平力使弹簧压缩,如图所示,当撤去外力后,下列说法中正确的是

[ ]

A.a尚未离开墙壁前,a和b系统的动量守恒

B.a尚未离开墙壁前,a与b系统的动量不守恒

C.a离开墙后,a、b系统动量守恒

D.a离开墙后,a、b系统动量不守恒

考点:动量守恒定律
题型:不定项选择

阅读理解.

     Jane always goes to school early. She likes to talk to her friends before class. After school she doesn’t go home early. She is always late. Jane stops to see the animals in the pet(宠物)shop. She likes to see the dogs. One of them is a little white dog. She watches the little dog play in the window of the shop. She

watches for a long time, so she comes home late.

     But one day, she doesn’t see the dog in the window of the shop. She is very unhappy.

     Her birthday comes. In the evening, mother shows(给……看)her a big birthday cake and father gives her a birthday surprise(惊喜).He gives her the little white dog. Jane is very happy.

     The next day, Jane doesn’t come home late.

1. Jane is a _____.

A. school boy

B. teacher

C. dog

D. school girl

2. Why is Jane always late for home?

A. She plays in the school

B. She stays in the classroom

C. She watches a little dog in a shop

D. She buys a little dog in a shop

3. When she can’t see the dog in the shop, she is ______ .

A. happy

B. glad

C. not happy

D. fine

4. Her mother gives Jane ______.

A. a cake

B. a dog

C. a surprise

D. a book

5. Jane doesn’t come home late from the next day, because ______.

A. she doesn’t like the dog

B. she can play with the dog at home

C. she doesn’t want to talk to her friends

D. her father and mother are at home

题型:不定项选择

分解因式:(1)36x3-9xy2;(2)-3a3+6a2b-3ab2

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我国的股票发行实行核准制并配之以发行审核制度和保荐制度。()

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请描述移动语音专线业务优势。

题型:不定项选择

不能产生协同作用的联合用药是()

A.磺胺药和TMP联合

B.阿托品和碘解磷定联合

C.四环素和青霉素联合

D.阿莫西林与庆大霉素联合

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