1. The problem statement, all variables and given/known data A particle of mass m is trapped in a one-dimensional infinite square well running from x= -L/2 to L/2. The particle is in a linear combination of its ground state and first excited state such that its expectation value of momentum takes on its largest possible value at t=0. 3. The attempt at a solution I know the process of solving PDE's clear as day, thats not the issue. The problem is that I'm tripping myself out on how to write Ψ(x,t) as a linear combination of its ground state + first excited state. My hunch is to approach the problem like this : Ψ(x,t)=c1Ψ1(x,t)+c2Ψ2(x,t) where 1 and 2 represent the ground state and first state, respectively that momentum takes on the largest possible value at t=0 is confusing and not sure what to do.