1-5 DDDBD
6-10 CBDDC
11-15 CBCBC
16, g=4Π2l / T2, AC, 图3，BC,√l ，4Π2/k2， C , 0.04
17. f=(4n+3)/0.12 Hz, n= 0,1,2….
V=40n+30 m/s , n= 0,1,2….
18. 0.3m/s，（0.8+n）m/s，n= 0,1,2….
19. 1m/s, 0.5m/s, 0.25J.
20. ![](https://wkrtcs.bdimg.com/rtcs/image?w=553.73&md5sum=92add4c5cbed4276d5303ff3877886ab&sign=f4d3dffc07&rtcs_flag=2&rtcs_ver=4&l=webapp&bucketNum=478&ipr={"t":"img","r":"r_27","w":"553.73","h":"297.00","dataType":"png","c":"word/media/image1.png","imgOriW":1238,"imgOriH":664})
![](https://wkrtcs.bdimg.com/rtcs/image?w=101.53&md5sum=92add4c5cbed4276d5303ff3877886ab&sign=f4d3dffc07&rtcs_flag=2&rtcs_ver=4&l=webapp&bucketNum=478&ipr={"t":"img","r":"r_27","w":"101.53","h":"100.13","dataType":"png","c":"word/media/image2.png","imgOriW":233,"imgOriH":229})
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