一列在竖直方向振动的简谐横波，波长为λ，沿正x方向传播，某一_爱下问搜题

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问题多选题

一列在竖直方向振动的简谐横波，波长为λ，沿正x方向传播，某一时刻，在振动位移向上且大小等于振幅一半的各点中，任取相邻的两点P₁、P₂，已知P₁的x坐标小于P₂的x坐标，（）

A．若，则P₁向下运动，P₂向上运动

B．若，则P₁向上运动，P₂向下运动

C．若，则P₁向上运动，P₂向下运动

D．若，则P₁向下运动，P₂向上运动

答案

AC

完形填空

An old man went to live with his son, daughter-in-law, and 4-year-old grandson. The old man’s hands    , his eyesight was not clear, and his    unsteady（不稳定的）. The family were    every night at the dinner table. But the elderly grandfather’s shaky hands and     sight made this rather difficult. Peas rolled off his spoon onto the floor. When he grasped the glass,       would often spill（洒落）onto the tablecloth. “We must do something about grandfather,” said the husband.
So the husband and wife set a small table in the corner. There, grandfather ate    in the corner while the rest of the family enjoyed dinner at the dinner table.       grandfather had already broken a dish or two, his food was served in a    bowl. Sometimes, when the family      grandfather, he had a tear in his eye as he ate alone.      , the only words the couple had for him were sharp    when he dropped a fork or spilled food. The 4-year-old boy watched all this      .
One evening before supper, the father      his son playing with wood scraps（小块）on the floor. He asked the child sweetly: “What are you making?” Just as      , the boy answered: “Oh, I am making a little    for you and mama to eat your food from when I grow up.” The 4-year-old boy smiled and went back to      on it.
The words    the parents so much that they were    . Then tears started to stream down their cheeks.        no word was spoken, both knew what they had to do. That evening, the husband took grandfather’s hand and      led him back to the family table.

C．disappearing

C．looked through

D．looked after

D．fortunately

单项选择题

慢性心房纤颤是指心房纤颤病史

A．大于24小时
B．大于1个月
C．大于3个月
D．大于48小时
E．大于3天，