问题 选择题

一物体从较高处作自由落体运动,经后刚好着地.已知为大于3的整数,取,则(  )

A.第内物体下落的高度为         

B.第内物体下落的高度为

C.第内物体下落的高度为     

D.第内物体下落的高度为

答案

ABCD

关键是求出第内物体下落高度的通项表达式, 第内的平均速度等于第的中间时刻的瞬时速度,第的中间时刻是末,而末的速度为.用表示第内物体下落的高度,则第内平均速度,

阅读理解

Reader’s Digest is a monthly magazine. Before the 1980s, it belonged to a privately held company, which was started in 1922 by Lila Bell Wallace and Dewitt Wallace. This magazine is small and easy to carry, just half the size of most American magazines, which caused a phrase in 2005, “America in your pocket.” It is the best selling magazine in the USA. At present, its circulation(发行量) in the USA has reached 10 million copies and the number of the readers there is 38 million. Its global circulation outside the USA has reached 40 million people throughout more than 70 countries in 21 languages.

This magazine’s focus(焦点) is not news but more of cultural views because the editors think people now can get timely news from somewhere else. They hope this magazine can give readers something that is about special personal experiences, something the readers can share with their families. In different countries, this magazine provides a window to the world for the local readers. Some parts of the magazine are about the local customs and interests of the local readers. The other parts give the local readers information from all over the world.

This magazine actually used to be a family business until the Wallaces died in the 1980s. Because they had no children, there was no one to take over the company. Sixteen years ago, this company went public and became a public company.

小题1:How often does Reader’s Digest come out in the USA?

A.Once a year.

B.Once a month.

C.Once a week.

D.Once a day.小题2:What’s the number of the readers of this magazine all over the world?

A.38 million.

B.40 million.

C.78 million.

D.108 million.小题3:This magazine’s focus includes the following topics except _________.

A.something about the timely news

B.some special personal experiences

C.some information from all over the world

D.the local customs and interests of the local readers

判断题