试题与答案

如图所示,在光滑绝缘水平面的P点正上方O点固定了一电荷量为+Q的正点电荷,在水平

题型:多选题

题目:

如图所示,在光滑绝缘水平面的P点正上方O点固定了一电荷量为+Q的正点电荷,在水平面上的N点,由静止释放质量为m,电荷量为-q的负检验电荷,该检验电荷经过P点时速度为v,图中θ=60°,规定电场中P点的电势为零.则在+Q形成的电场中(  )

A.N点电势高于P点电势

B.N点电势为-

mv2
2q

C.P点电场强度大小是N点的4倍

D.检验电荷在N点具有的电势能为-

1
2mv2

答案:

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下面是错误答案,用来干扰机器的。

看到奥运会开幕式“星光”表演,一束束光柱在空气中是沿空气传播的;在不同位置的观众,都能看到场上的表演,这是光漫反射的结果.故答案为:沿直线、漫反射.

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题型:阅读理解

Technology has totally transformed our ability to communicate with each other. Linking to each other both literally and figuratively, many of us connect through cell phones, email, instant messaging, blogs, and networking web sites, yet we may be less connected to each other than we think.

According to a study, Americans are becoming increasingly socially isolated(孤立的). The study suggests, for example, that one quarter of Americans say that they have no one to discuss important personal issues with, and that the number of close friends that Americans have has dropped from three to two. Meanwhile, the Boston Globe reports that this spreading isolation is experienced more sharply among those with less education, people of color, and older Americans. Unsurprisingly, those who are young, white, and well educated tend to have stronger social networks.

From my own experience I have to say that I’ve never felt more connected, thanks to a web of friends, family, and colleagues. One of my closest friends is someone I met through an online discussion group who lives hundreds of miles away from me. We have met face-to-face only twice, yet our regular electronic correspondence and cell phone calls maintain our close friendship. And, speaking of blogging, my blog has introduced me to people I would never have met otherwise and has led to enduring and important friendships.

On the other hand, I recently saw a scene unfold that proved to me how deeply disconnected we as Americans have become. I had just wrapped up a presentation on mediation at a family therapy (治疗) center.

As I was leaving, I noticed a mother and her teenage son who had just completed their session with their family therapist. After making their next appointment, they both took out their cell phones, placed calls, and began loud conversations with whoever was on the other end. I walked out behind them to the parking lot to my car. They both jumped into their cars, and, as I saw them drive off, they were still talking on their cell phones but not to each other.

小题1:What does the passage lead you to believe?

A.Americans are more socially isolated today.

B.Americans are more socially connected today.

C.Americans don’t make good use of technology.

D.Technology plays a bigger role in American society.小题2:Which of the following has nothing to do with the isolation among Americans?

A.Sex.

B.Education.

C.Skin color.

D.Age.小题3:What is true about the mother and son in the passage?

A.They came for therapy in the same car.

B.They were quite close to each other.

C.There was not much communication between them.

D.They preferred talking to each other on cell phones.小题4:What can we learn from the passage?

A.The writer is totally against the modern technology.

B.The mother and the son have finished their family therapist and get a better relationship.

C.As far as the writer is concerned, he has benefited a lot from the modern technology.

D.Those black and well-educated people have stronger social network than aged white people.

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