图12-2-8所示为某一时刻简谐波的图象，波的传播方向沿x轴正方向，下述说法正确的是（ ）
图12-2-8
A．质点a、b的振幅相等
B．该时刻质点b、e的速度相同
C．该时刻质点c、f的加速度为零
D．该时刻质点d正向下运动
AD
该时刻波的图象中a、b质点位移不同，但对简谐波来说，各质点的振幅都是相等的，选项A正确.质点b速度方向向上，而e质点速度方向向下，它们此时刻速度不同，选项B是错的.质点c位移为负的最大值，回复力为正的最大值，加速度也为正的最大值；质点f位移为正的最大值，其回复力和加速度都为负的最大值，C错误，d质点的运动方向是向下的，D正确.
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| A shopkeeper closed his shop in the evening and went home. He was very 1 , but just as he went to 2 , the telephone rang. A man's 3 said, "What time do you open your shop, sir?" The shopkeeper was 4 about the phone call. He did not answer it and went 5 to bed. A few minutes later, the telephone 6 . He got up and went to pick up the phone and found that 7 was the same man asking the same question. The shopkeeper angrily answered,"You needn't ask me that for (因为) I 8 tonight. It's late." " 9 , I want to go 10 ," the man said. | ||||
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