Before a signal reaches the wall, the portion to the right of the leading characteristic $x=c_0t$ is unaffected. Its initial depth and velocity persist, giving $\boxed{u=0,\qquad c=c_0\quad(c_0t\leq x\leq a)}$ for $0\leq t\leq a/c_0$.


Solution

Past exam of the mathematics course of the University of Cambridge / 2015 / ii / Paper 4 / 36B / i / Solution

 Solution (source code)