# Quantum Mechanics "Expectation"

by roshan2004
Tags: expectation, mechanics, quantum
 P: 139 1. The problem statement, all variables and given/known data 1. Calculate the expectation value  of the momentum of a particle trapped in a one-dimensional box. 2. Find the expectation value of the position of a particle trapped in a box L wide. 2. Relevant equations $$\psi _{n}=\sqrt{\frac{2}{L}}sin \frac{n\pi x}{L}$$ $$=\int \psi^*p_{x}\psi dx$$ $$=\int \psi^*x\psi dx$$ 3. The attempt at a solution I got confused on choosing the limits for both the problems for integrating them. What's the limits I should chose for both the problems.
 Mentor P: 40,708 Where is Ψ non-zero? (What are the boundaries of the box?)
 P: 139 x=0 and x=L
P: 139

## Quantum Mechanics "Expectation"

Thanks I got it. The limits that I have to use are x=0 and x=L
 Mentor P: 40,708 Exactly.

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