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问题 选择题

关于力的合成，下列说法正确的是（   ）

A．一个物体受两个力的作用，求出它们的合力，物体便受到三个力的作用

B．如果一个力的作用效果与几个力的作用效果相同，这个力就是那几个力的合力

C．不同性质的力，不能进行合成

D．某个力与其他几个力使物体发生的形变相同，这个力就是那几个力的合力

答案

BD

合力与分力是等效代替关系，合力产生效果与分力共同作用的效果相同，不涉及性质问题，故B、D对.

填空题

-个练习本的单价是a元，买b本，应付______元．
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改错题

Dear Frank,

I’m writing to tell you anything about my university(大学) life. It is three months since I come here. I have never left my parents for so long, but I miss them very much. At first it was difficult to me to do everything on my own, but now I am used to the life here. As for study, I major in (主修)the English because Englishis my favorite subject. I have made much good friends, one of whom is Jim, the more intelligent student in my class. He always has some good opinion and he is thought high of (高度评价)by others.

I am sorry but I must stop now. Please writing to me when you are free.
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