Question

麻烦大神们给说下解题过程！大物好难啊啊~~要考试了，急急急~！！！过程清晰的话会再追加悬赏，谢谢谢！

只做用蓝色笔画出来的就好了~麻烦优先解决星标题，谢谢谢

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Answer 1

ω=2π/T=200π
t=0,y=0,Vy>0--->φ=-π/2
y(x,t)=Acos(ω(t-x/u)+φ)=0.1cos(200π(t-x/400)-π/2)

追问

请问回答的哪道题啊~~来不及一个一个对了

追答

最后一个

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 能麻烦你把其他的题都做下么，拜托啦，我把所有财富值都给你

追答

1. v=1260m/s,f=2000Hz--->λ=v/f=0.63m

   Δφ=(2π/λ)Δx=(2π/λ)*0.21=2π/3

   Δt=Δx/v=0.21/1260=0.167ms

2. λ=5m,v=8m/s-->f=v/λ=1.6Hz

   y(t)=Acos(ωt+φ)=Acos(2πft-π/2)=Acos(3.2πt-π/2)

   y(x,t)=Acos(3.2π(t-x/8)-π/2)

   x=3m,y(t)=Acos(3.2π(t-3/8)-π/2)

3. x=0,A=-2A/2,v<0--->φ=2π/3

   Δx=3,Δφ=π-2π/3=π/3

   λ=2πΔx/Δφ=18m

   v=λf=18*2.5=45m/s

   y(x,t)=Acos(2πf(t-x/v)+2π/3)=Acos(5π(t-x/45)+2π/3)

   Xp=3+9=12m

   y(t)=Acos(5π(t-9/45)+2π/3)