题干

如图所示,真空中有一匀强电场(图中未画出),电场方向与圆周在同一平面内,△ABC是圆的内接直角三角形,∠BAC=63.5°,O为圆心,半径R=5cm.位于A处的粒子源向平面内各个方向发射初动能均为8eV、电荷量+e的粒子,有些粒子会经过圆周上不同的点,其中到达B点的粒子动能为12eV,达到C点的粒子电势能为﹣4eV(取O点电势为零).忽略粒子的重力和粒子间的相互作用,sin53°=0.8.下列说法正确的是(   )

A:圆周上A,C两点的电势差为16V

B:圆周上B,C两点的电势差为﹣4V

C:匀强电场的场强大小为100V/m

D:当某个粒子经过圆周上某一位置时,可以具有6eV的电势能,且同时具有6eV的动能

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答案(点此获取答案解析)

C,D

同类题3

阅读下面短文,从短文后各题所给的A、B、C和D四个选项中,选出可以填入空白处的最佳选项。

    In spite of the fun and laughter, 13-year-old Frank Wilson was not happy. It was 1 that he received all the presents he wanted. And he also 2 the big Christmas dinner with family members.3, Frank was not happy because this was his first Christmas without his brother, Steve, who during the year, had been killed in a car accident. Frank 4 his brother.

    Frank said good-bye to his relatives, and explained to his parents that he was going to see a friend. Since it was cold outside, Frank 5 his new plaid jacket. It was his favorite gift. He placed the other presents on his new sled (雪橇). Then Frank 6.

    As Frank went down the street toward home, through one front window, he saw a room with old 7 hanging over an empty fireplace. A woman was seated nearby, crying. The stockings 8 him of the way he and his brother always 9 theirs side by side. The next morning, they would find presents.

    Then Frank had a10. He knocked on the door. “Yes?” the 11voice of a woman asked. “May I come in?” asked Frank. “You are very welcome,” she said.12his sled full of gifts and thinking he wanted to 13 gifts. “But I have no food or gifts for you. I have 14 for my own children.” “That's not why I am here,” Frank replied. Please 15 whatever presents you would like for your children from the sled.” “Why, God bless you!” the 16 woman answered gratefully. She selected some candies, a toy airplane and a doll. Finally, the stockings were 17. “Thank you so much!” the woman Said. “You are welcome,” Frank said and left.

    Frank's18was full of happiness. Then he gave his jacket to a poor boy. At last, he19 all his gifts. Now Frank was worried how he could 20 to his parents that he had given his presents to others.