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问题 选择题

如图所示，有5000个质量均为m的小球，将它们用长度相等的轻绳依次连接，再将其左端用细绳固定在天花板上，右端施加一水平力使全部小球静止．若连接天花板的细绳与水平方向的夹角为45°．则第2011个小球与2012个小球之间的轻绳与水平方向的夹角α的正切值等于（　　）

A．

2989
5000

B．

2011
5000

C．

2011
2089

D．

2089
2011

答案

以5000个小球组成的整体为研究对象，分析受力情况，如图1所示，根据平衡条件得

    F=5000mg

再以2012个到5000个小球组成的整体为研究对象，分析受力情况，如图2所示，则有

   tanα=

2989mg
F
=
2989
5000

故选A

选择题

Mobile phones are very popular now and they aremuch        than before.[ ]

A. cheap

B. cheaper

C. cheapest

D. the cheapest
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单项选择题

The following data sufficiency problems consist of a question and two statements, labeled (1) and (2), in which certain data are given. You have to decide whether the data given in the statements are sufficient for answering the question. Using the data given in the statements plus your knowledge of mathematics and everyday facts (such as the number of days in July or the meaning of counterclockwise), you must indicate whether.

A farmer sells buckets of onions for $2, buckets of potatoes for $4, and buckets of squash for $5. How many buckets of squash did the farmer sell ？（）
(1) The farmer sold one bucket of onions.
(2) In total, the farmer sold 7 buckets of produce for $33.

A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.

B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.

C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.

D. EACH statement ALONE is sufficient.

E. Statements (1) and (2) TOGETHER are NOT sufficient.
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