A perfectly elastic string of equilibrium length L is released from the initial shape
with an initial velocity profile
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The string is clamped at both ends (x = 0 and x = L).
Waves move on the string with speed c.
There is no friction.
Determine the subsequent evolution of the displacement
y(x, t) of the string.
The governing partial differential equation is
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The complete solution is the sum of a pair of Fourier sine series
in x.
However, only one term in each series is non-zero (see the lecture notes).
The complete solution is simply
![]()

This plot is for L = 4 and c = 1.
The Maple file is available here.