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问题 选择题

一带电小球用丝线悬挂在如图所示的水平匀强电场中静止．现在烧断悬线，小球接下来将会立即做（　　）

A．自由落体运动

B．曲线运动

C．沿着悬线的延长线作匀加速运动

D．变加速线运动

答案

悬线烧断前，小球受重力、拉力、电场力平衡，重力和电场力的合力与拉力等值反向．烧断细线，物体受重力、电场力，两个力合力恒定，沿细线方向，小球开始静止，在恒定合力作用下将沿合力方向即沿着悬线的延长线方向做匀加速直线运动．故C正确．A、B、D错误．

故选C．

选择题

When it grows ________, it will grow ________ a strong animal.

A．up; up

B．up; into

C．into; into

D．into; with
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填空题

a. How could I excite my students and show my warmth, so that they could enjoy their study in English I had a deep thought. b. In order to save my face,I just criticized them seriously whenever they talked in class or even moved a little c. It was smile. There was a kindness called smile. It was the most beautiful language in the world. It could make distance disappear. d. Then I realized my frozen eyes made the students seared and my aerious face took any excitement away from the children’s hearts. e. The next day,I stood on the stage with a smiling face, asking questions with a smile and encouraging the children in a friendly way. I could find happiness and excitement in their eyes ! f. I could control the class now, but the atmosphere became strange. No, they were not listening to me. g. It was too quiet. The breathless silence urged me to consider the way I was teaching. h. I remember,five years ago, when I stood at the teacher’s desk for the first time, the students in my class paid no attention to me,didn’t behave themelves at all. I felt helpless. i. Gradually,they got used to my smile and encouragement. The class became a lovely one. I was moved,and said , "Thank you for listening,boys and girls!" j. "Just awake the students with a smiling face"I said to myself.

________
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