So if we have a particle in a one dimensional box with walls at x=0 and x=a. Now suppose one of the walls is moved in a time short compared to the natural period 2pi/w1, where (h/2pi)w1=E. If the energy of the particle is measured soon after this expansion, what value of energy is most likely to be found. How does this energy compare to the particle's initial energy E1? Help anyone? I am not sure how to go about solving this. I usually use the equation Psi(x,0)= the integral of b(k)(Psik)dk where Psik=(1/square root of (2pi))exp(ikx) But since I am not told what Psi(x,0) is, there is no way for me to solve for b(k). Am I just interpreting this problem completely wrong?