Wave equation: intial conditions

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SUMMARY

The discussion centers on solving the initial boundary value problem defined by the wave equation \( u_{tt} = c^2 u_{xx} \) with boundary conditions \( u(-a,t) = 0 \) and \( u(a,t) = 0 \), and initial condition \( u(x,0) = \sin(\omega_1 x) - b \sin(\omega_2 x) \). Participants question whether the provided initial and boundary conditions are sufficient for a complete solution, noting that typically, a second-order partial differential equation requires four conditions. The consensus suggests that assuming \( u_t(x,0) = 0 \) may be necessary to fully resolve the problem using d'Alembert's solution.

PREREQUISITES
  • Understanding of wave equations, specifically \( u_{tt} = c^2 u_{xx} \)
  • Familiarity with boundary value problems and initial conditions
  • Knowledge of d'Alembert's solution for wave equations
  • Basic principles of partial differential equations (PDEs)
NEXT STEPS
  • Study the derivation and application of d'Alembert's solution for wave equations
  • Research the implications of boundary conditions in solving PDEs
  • Explore methods for determining initial conditions in wave problems
  • Examine examples of second-order PDEs and their required conditions for solutions
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Students and educators in mathematics, particularly those focusing on differential equations, as well as researchers and professionals dealing with wave phenomena in physics and engineering.

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Homework Statement



Solve the initial boundary value problem

[tex]u_{tt}=c^2u_{xx}[/tex]
[tex]u(-a,t)=0,\quad u(a,t)=0,\quad u(x,0)=\sin(\omega_1 x)-b\sin(\omega_2x)[/tex]

where [itex]a, b, \omega_1, \omega_2[/itex] are positive constants.

Homework Equations



d'Alembert's solution

The Attempt at a Solution



Are these initial/boundary conditions enough to fully solve the problem? All of the textbooks I have seen address only the case where [itex]u(x,0)[/itex] and [itex]u_t(x,0)[/itex] is also given. Or possibly d'Alembert's general solution is not good to use here? Thanks all!
 
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A second order partial differential equation requires four boundary conditions in order to be fully solved, so it might be the case that you are meant to assume that ut(x,0)=0. Is that all of the information the question gives you?
 

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