题干

如图所示,空间中A、B、C三点的连线恰构成一直角三角形,且∠C=30°,AB=L,在B、C两点分别放置一点电荷,它们的电量分别是+Q与-Q(静电力常量为k).求斜边AC的中点D处的电场强度.

上一题 下一题 0.0难度 选择题 更新时间:2018-10-28 10:17:47

答案(点此获取答案解析)

解:∠C=30°,连接BD , 由几何关系可知:BD=CD=AB=L;所以点电荷+Q与-Q在D处产生的场强大小相等,大小为 E=k
Q
L
2
,方向如图所示:

同类题4

阅读下面短文,掌握其大意,然后从各题所给的四个选项(A、B、C和D)中,选出最佳选项。

    I often read of incidents of misunderstanding or conflict. I'm left1.Why do these people create mistrust and problems, especially with those from other2?

    I was growing up in Kuala Lumpur in the early 1960s,3children from different races and religions played and studied4in harmony. At that time my family lived a stone's5from Ismail's. And no one was bothered that Ismail was a Malay Muslim and I was an Indian Hindu-we just6our differences. Perhaps, our elders had not filled our heads with unnecessary advice, well7or otherwise.

    We were nine when we became friends. During the school holidays, we'd8the countryside on our bicycles, hoping to9the unexpected. At times Ismail would accompany my family as we made a rare shopping trip to town. We would be glad of his10.

    When I was twelve, my family moved to Johor. Ismail's family later returned to their village, and I11touch with him.

    One spring afternoon in 1983, I stopped a taxi in Kuala Lumpur. I12my destination. The driver acknowledged my13but did not move off. Instead, he looked14at me. “Raddar?”he said, using my childhood nickname(绰号). I was astonished at being so15addressed(称呼). Unexpectedly! It was Ismail! Even after two16we still recognized each other. Grasping his shoulder, I felt a true affection, something17to describe.

    If we can allow our children to be18without prejudice, they'll build friendships with people, regardless of race or religion, who will be19their side through thick and thin. On such friendships are societies build and20we can truly be, as William Shakespeare once wrote, “we happy few, we band of brothers”.