问题 选择题

一物体静止在水平桌面上,则下列说法正确的是

A.桌面对物体的支持力与物体所受的重力是一对平衡力

B.物体对桌面的压力就是物体的重力,它们的性质相同

C.物体对桌面的压力与桌面对物体的支持力是一对作用力与反作用力

D.物体对桌面的压力与桌面对物体的支持力是一对平衡力

答案

AC

题目分析:物体处于二力平衡状态,选项A正确。物体对桌面的压力性质上是弹力,物体的重力与这个弹力是不同性质的力,选项B错误。物体之间的作用力与反作用力总是相互的,选项C正确。平衡力必须具有相同的受力物体,选项D错误。

填空题
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                                              High Speed Book Scanner

     Simply turning pages of a book quickly may not seem like the best way to scan it. A Japanese

research group at Tokyo University has created new software that allows hundreds of pages to be

scanned within minutes. Scanning text is normally a boring process with each page having to be inserted

into a scanner, but the team led by Professor Masatoshi Ishikawa uses a high speed camera that takes

500 pictures a second to scan pages as they are turned by workers.

     Normal scanners can only scan the information that is actually before them on the page. This high

speed book scanner uses a camera that captures pages at 1000fps as they are turned. A system built in

allows it to automatically correct any changes to the text due to the page bending as well as light differences due to shadows. "It takes a shot of the shape, then it calculates the shape and uses those calculations to

film the scanning," Ishikawa said, explaining the system used to reconstruct the original page.

     The current system is able to scan an average 250-page book in a little over 60 seconds using basic

computer hardware. While it now requires extra time to process the scanned images (影像), the

researchers hope to eventually make the technology both faster and much smaller. "In the more distant

future, once it becomes possible to put all of this processing on one chip (芯片) and then put that in an

iPad or iPod, one could scan just using that chip. At that point, it becomes possible to scan something

quickly to save for later reading," Ishikawa said.

     Being able to scan books with an iPhone may be further off, but Ishikawa says that a commercial

version of the large-scale computer based scanning system could be available in two or three years.

While the technology has the potential to take paper books into the digital age, it remains to be how

publishers will react to people scanning their books while just turning pages quickly.

1. According to the passage, the advantage of the new scanning software is that ______.

A. there is no need to scan every page

B. it can work much more effectively

C. no manpower is needed in operating the scanner

D. it can make the scanning process more interesting

2. According to Ishikawa, the scanner works by_____.

A. changing the shape of the images        

B. reducing the size of the images

C. reconstructing the original page          

D. scanning several pages at the same time

3. What is Ishikawa's attitude towards the development of the scanning system?

A. Optimistic.        

B. Uncertain.        

C. Disapproving.        

D. Cautious.

4. What does the underlined sentence mean?

A. People will get any book they like more easily.

B. Publishers will refuse to comment on the new software.

C. Publishers will probably not welcome the new software.

D. People won't need to buy books any more with an iPhone.