一弹簧振子做简谐运动,周期为T,下列说法正确的是.( ) A.若△t=T2,则在

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问题:

一弹簧振子做简谐运动,周期为T,下列说法正确的是.(  )

A.若△t=

T
2
,则在t时刻和(t+△t)时刻振子速度的大小一定相等

B.若△t=

T
4
,则t和(t+△t)两时刻,振子的位移大小之和一定等于振幅

C.若t时刻和(t+△t)时刻振子对平衡位置的位移大小相等,方向相同,则△t一定等于T的整数倍

D.若t时刻和(t+△t)时刻振子运动速度大小相等,方向相反,则△t一定等于

T
2的整数倍

考点:简谐运动的振幅简谐运动的周期、频率和角频率
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100克和100厘米一样大。[ ]

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第四部分  短语和单词拼写(满分20分)

1. 与…进行来往___________________    2. 把基因插入受体细胞 _____________

3. 挤进人群  _____________            4. 用脚打拍子         ____________

5. 与…一致;和…一样____________     6. 扑倒在…上    _________________

7. 在…方面有所突破  _____________    8. 一成不变的生活   ______________

9. 伴着音乐跳舞____________________   10. 向…宣战      _______________

11. The cross is s______________ of Christianity(基督教).

12. There are many different pipa schools and each one has its special way of ____(诠释)the classical pieces.

13. The emotional and mental problem a_________ from her physical cause.

14. He has said nothing r___________ your request.

15. Farmers think it would be handy to clone a prize cow which can resist b__________ or disease.

16. She worked hard to practice singing. E            she won the first prize in the singing contest.

17. Teachers often _____________(鼓励)their students to fight for their bright future.

18. Down there on the pavement, few __________ (过路人) stop.

19. The milk is __________ (怀疑)of causing over 200 deaths.

20.We’re all ___________ (厌恶)at the way her husband has treated her.

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简述农业推广项目选择的原则。

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热制度由铁水含硅量和()体现。

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支抗设计在与矫治牙的同一牙弓内,利用一些牙作为支抗而使其他一些矫治牙移动,这种支抗是

A.颌间支抗

B.黏膜支抗

C.枕部支抗

D.颌内支抗

E.颌外支抗

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