搜题请搜索小程序“爱下问搜题”
问题 选择题

下列现象中，由地球自转产生的是（　　）

A．四季变化

B．昼夜长短不同

C．昼夜更替

D．正午太阳高度不同

答案

地球自转产生的现象是昼夜交替和时间差异；地球围绕太阳公转产生了四季变化、正午太阳高度的变化、昼夜长短的变化以及地球五带等现象．根据题意．

故选：C．

填空题

Part 4


Questions 26-45


·Read the following text and decide which answer bestfits each space.
·For questions 26-45, mark one letter A, B, C or D on the Answer Sheet.

Newspapers


Who won the World Cup 1994 football game What happened at the United Nations How did the critics like the new play When an event takes place, newspapers are on the streets (26) the details. (27) anything happens in the world, reporters are on the spot to (28) the news.
Newspapers have one basic (29) to get the news as quickly as possible from its source, from those who make it to those who want to (30) it. Radio, telegraph, television, and (31) inventions brought competition for newspapers. So did the development of magazines and other means of communication. (32) this competition merely spurred the newspapers on. They quickly made (33) of the newer and faster means of communication to improve the speed and (34) the efficiency of their own operations. Today more newspapers are printed and read than ever before.
Competition also led-newspapers to branch out into many other fields. Besides keeping readers (35) of the latest news, today’s newspapers (36) readers about politics and other important and serious matters. Newspapers influence readers’ economic choices (37) advertising. Most newspapers depend on advertising for their very (38) Newspapers are sold at a price that (39) to cover even a small fraction of the cost of production. The main (40) of income for most newspapers is commercial advertising. The (41) in selling advertising depends on a newspaper’s value to advertisers. This is measured (42) circulation. How many people read the newspaper Circulation depends (43) on the work of the circulation department and on the services or entertainment (44) in a newspaper’s pages. But for the most part, circulation depends on a newspaper’s value to readers as a source of information (45) the community, city, country, state, nation, and world—and even outer space.

A. Therefore B: Although C. OtherwiseD. However
查看答案
实验题

根据打出的纸带，如图，选取纸带上打出的连续五个点A、B、C、D、E，测出A点距起点O的距离为x0，点A、C间的距离为x1，点C、E间的距离为x2，交流电的周期为T，则根据这些条件计算重锤下落的加速度a的表达式为：a＝________。

(2)在“验证机械能守恒定律”的实验中发现，重锤减少的重力势能总是大于重锤增加的动能，其原因主要是因为在重锤下落过程中存在着阻力的作用，我们可以通过该实验装置测定该阻力的大小．若已知当地重力加速度为g，还需要测量的物理量是________(写出名称和符号)，重锤在下落过程中受到的平均阻力的大小F＝________。
查看答案