问题 选择题

如图所示是阴极射线示波管的聚焦电场。实线为电场线,虚线为等差等势线。a、b、c为从左侧进入聚焦电场的电子运动的轨迹上的三点。不计电子的重力,则

A.电场中a点的电势高于c点的电势

B.电子经a点的动能大于经c点的动能

C.电子经b点的加速度大于经c点的加速度

D.电子经b点的电势能大于经c点的电势能

答案

CD

题目分析:沿电场线方向电势降低,故a点的电势低于c点的电势,A错误;电子由a点运动到c点的过程中,电场力做正功,电势能减小,动能增大,故B错误D正确;等差等势面密集处电场强度大,故电子受到的电场力大,加速度大,故C正确。

单项选择题
阅读理解

Riding a London subway, a person from other countries will notice one major difference: in London, people do not look at each other.In fact, eye contact is avoided at all times. That’s not rudeness ― people are just too busy to bother looking.

  Busy doing what, you ask? Well, they’re certainly not using the time for a moment of quiet thinking.Nor are they reading a book.New technology has replaced quiet habits.Today the only acceptable form of book on the London underground is an e-book.

  Apple must earn a fortune from London commuters(使用月票上下班者). Since the launch of the iPhone in 2007, over 40, 000 ― yes, 40, 000 “apps” have been designed.

  Commuters love them because they are the perfect time - fillers. One “app”, called iShoot, is a game that features tanks.Another one, Tube Exits, tells passengers where to sit on the train to be closest to the exit of their destination. iSteam clouds the iPhone screen when you breathe into the microphone. You can then write in the “steam” on your phone screen.

  For those without an iPhone, another Apple product, the iPod, may be the distraction (消遣) of choice. It’s not just teenagers who “plug in” to their music - iPods are a popular way to pass the time for all ages.

  And if games, e-books and music aren’t enough to keep you occupied, then perhaps you would prefer a film? The development of palm DVD technology means many commuters watch their favorite TV shows or films on the way to work.With all these distractions, it’s amazing that people still remember to get off the train.

小题1:Those who want to save time to reach where they go can download ________ to their iPhones

A.iShoot

B.Tube Exits

C.iSteam

D.iPod小题2:People in London do not make eye contact on the subway because ________.

A.they are going to work and have no time to communicate with each other

B.they love reading books and do not want to be disturbed

C.they feel sleepy because of getting up early

D.they’re busy playing games, reading e-books, listening to music or watching films小题3:The underlined word “apps” in the third paragraph means ________.

A.computers

B.programs downloaded for the iPhone

C.computer companies

D.fortune from London commuters小题4:The main idea of the passage is that ________.

A.London commuters are unfriendly to strangers

B.Apple has earned a lot of money from selling 40, 000 apps

C.technology is changing how London commuters spend their traveling time

D.riding a London subway is a must when visiting London