Solving for non moving points of a 1-D wave

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SUMMARY

The discussion focuses on identifying non-moving points on a 1-D wave represented by the function u(x,t) = sin(πx)cos(πt) + (1/2)sin(3πx)cos(3πt) + 3sin(7πx)cos(7πt). To find these points, participants derive the condition for zero velocity by setting the time derivative of u(x,t) to zero. The key takeaway is that non-moving points occur where the amplitude is constant over time, leading to the equation -πsin(πx)sin(πt) - (3/2)π(3sin(πx) - 4sin³(πx))(3sin(πt) - 4sin³(πt)) = 0. The discussion emphasizes the need for systematic mathematical approaches rather than graphical approximations.

PREREQUISITES
  • Understanding of wave equations and their physical implications.
  • Familiarity with trigonometric identities and derivatives.
  • Proficiency in calculus, particularly in solving differential equations.
  • Experience with mathematical software like Maple or Mathematica for polynomial factorization.
NEXT STEPS
  • Study the derivation of wave equations in physics, focusing on boundary conditions.
  • Learn how to apply trigonometric identities to simplify complex expressions.
  • Explore polynomial factorization techniques using software like Maple or Mathematica.
  • Investigate the implications of stationary points in wave mechanics and their physical significance.
USEFUL FOR

Students and educators in physics and mathematics, particularly those studying wave mechanics, calculus, and differential equations. This discussion is also beneficial for anyone seeking to deepen their understanding of stationary points in wave functions.

  • #31
yes heh, considering I don't know how to get maple to do anything correctly, what are some alternatives to find the roots? Thanks
 
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  • #32
Well, the expression In post #18 is fully factored...that means that the roots of the ugly factor are going to be difficult to find...BUT! you don't need to find them because they will all depend on \beta, whioch means they will only be roots for certain values of t, and as I said in post #28, that means that those roots are not stationary points...do you not understand this?
 
  • #33
yes but...so am I suppose to say that even though they seem to be stationary, that's not the case since they will be dependent on beta?
 
  • #34
Why do you say "they seem to be stationary"?
 
  • #35
That's because we were to graph 10 plots at various t, I decidedly went t=1..10 and from the graphs the roots looked stationary

Also I had the impression that the problem would've been simpler in terms of all the trig stuff...
 
  • #36
Oh...try graphing it for t=0.2 and t=0.4...do they still look stationary?
 
  • #37
It definitely does not. So I did a bad job in choosing the appropriate time interval then? My graphs definitely made me think I'd be getting answers for nonmoving x values...
 
  • #38
regardless... Thank you very much for being so patient. It makes sense how you approached this problem now. once again, Thanks! :P
 

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