一列列简谐横波沿x轴负方向传播，周期为0.2s，某时刻波形如图所示，介质中质点a、b的平衡位置距原点O的距离分别是8cm和16cm，则该时刻有（ ）
A．a质点正在沿x轴的负方向运动
B．b质点的加速度方向沿y轴的正方向
C．该波的波速为1 m/s，故经t=0.08s，b质点将向x轴负方向运动0.08m的距离
D．从该时刻起，第一次质点a的运动状态与该时刻质点b的运动状态相同时，所经历的时间为t=0.08s
答案：D
本题考查机械波。由波的传播方向和质点的振动方向之间的关系可知a质点正沿x轴正方向振动，A错；质点b在平衡位置上方，所以加速度指向y轴负方向，B错；波传播过程中质点在各自平衡位置附近振动，并不随波迁移，C错；由图知波长
，波速
，波从b传到a所需时间
，D对。选D。
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| Grandfather's Clock In the dining room of my grandfather's house stood a heavy grandfather's clock.Meals in the dining room were a __1__for our four generations to become one.The grandfather's clock always stood like a trusted old family friend,__2__us playing jokes and telling stories,which was already a __3__of our life. As a child,the old clock interested me.I watched and listened to it during __4__.I was surprised how at __5__times of the day,the clock would strike three times,six times or more,with a wonderful great __6__ that echoed(回音)throughout the house.The clock chimed year after year,a part of my __7__,a part of my heart. Even more __8__to me was my grandfather's special action each day.He carefully __9__the clock with a special key each day.The key was magic to me.It __10__our family's magnificent clock ticking and __11__all year round. After my beloved grandfather died,it was several days after the __12__before I remembered the clock!"Mama!The clock has wound down!"The __13__washed my cheeks when I entered the dining room.The clock stood hopelessly as serious and __14__as the funeral ceremony had been.Not quite as magnificent without my grandfather's __15__touch.I couldn't bear looking at it. Years later,it worked again.In the movement of the hands of the clock,my grandfather lived again. | |||
| ( )1. A.time ( )2. A.seeing ( )3. A.start ( )4. A.stories ( )5. A.busy ( )6. A.shock ( )7. A.memories ( )8. A.comfortable ( )9. A.opened ( )10. A.made ( )11. A.singing ( )12. A.funeral ( )13. A.tears ( )14. A.attractive ( )15. A.brave | B. possibility B. hearing B. part B. jokes B. urgent B. sound B. minds B. hopeful B. wound B. controlled B. standing B. death B. sweats B. quiet B. special | C. problem C. watching C. signal C. periods C. happy C. song C. comfort C. wonderful C. turned C. kept C. knocking C. generation C. hair C. noisy C. kind | D. pleasure D. looking D. mark D. meals D. different D. music D. information D. skillful D. started D. fixed D. striking D. ceremony D. water D. magnificent D. strong |