问题 选择题

一匀强电场的电场强度E随时间t变化的图象如图所示,在该匀强电场中,有一个带电粒子在t=0时刻由静止释放,若带电粒子只受电场力作用,则下列说法中正确的是(  )

A.带电粒子只向一个方向运动

B.0~2s内,电场力做正功

C.2s末带电粒子回到原出发点

D.4s末带电粒子回到原出发点

答案

带电粒子在t=0时刻由静止释放,在0-1s内带电粒子沿着电场力方向做匀加速直线运动,

1-2s内沿原方向做匀减速直线运动,2s末速度减为零;

2-3s内沿反方向做初速度为零的匀加速直线运动,

3-4s内继续做匀减速直线运动,4s末速度减为零,回到出发点.

A、由上分析可知,带电粒子做往复运动.故A错误.

B、0~1s内电场力做正功,1~2s内电场力做负功.故B错误.

C、D,2s末带电粒子离原出发点最远,4s末带电粒子回到原出发点.故C错误,D正确.

故选D

阅读理解

1990 was a significant year in world enents. In Febbruary, Nelson Mandela was set free after 27 years in prison. In October, East and West Germany became one country again. Then at the end of 1990, the World Wide Web was born. For this final event we have one man to thank, Tim Berners-Lee, the father of the Web.

Berners-Lee was born on June 8, 1955 in London, England. His parents, both computer designers, encouraged him to think and work creativelhy as he grew up. He was an excellent student and naturally took an interest in computers and science.

After graduating from Oxford University, Tim went to work at a science research centre in Sfwitzerland. There be developed some of the different systems that would later become the Web. The first was HTML, the computer language used to make web pages. The second was an address system that let  computers anhywhere find each other and send and receive information. In 1990, while still at the science centre in Switzerland, he put them together to make the first Internet browser. It could run on any computer and allowed people to create  share their information with the rest of the world.

Tim knew that the more people used the Web, the more useful it would be. He wasn’t interested in money but knowledge, so he gave out his invention for free to anyone who was interested. Many were interested and the growth of the Internet began.

Today Tim works as a professor at the MIT in America, researching new and interesting ways to use the Web. He has received many awards from governments and organizations for his efforts. He is still not very interested in money. That is why he is so admired by his students and workmates. It may also be one of the reasons that few people outside the world of technology know his name.

小题1: The underlined word “significant” (in Paragraph 1) most probably means “       ” .

A.strange

B.terrible

C.important

D.difficult小题2:Which of the following statements is true according to the passage?

A.The address system was used to make make web pages.

B.The World Wide Web was created in Swizerland.

C.The fist web browser was very expensive to buy

D.Many people could use the Internet before 1990小题3: What can we learn about Berners-Lee from the passage?

A.He was encouraged to be creative.

B.He didn’t do well at school.

C.He is a very poor businessman.

D.He is well-known all over the world.小题4: Where does Berners-Lee live today?

A.England.

B.Switzerland.

C.America.

D.Canada.小题5:What is the passage mainly about?

A.The events that took place in 1990.

B.The history of the Internet.

C.The invention of the Internet browser.

D.The man who created the World Wide Web.

问答题