(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

What is the expectation value of <p*x> aka the momentum times the position operator, for a particle in a box.

2. Relevant equations

Psi(x) = root(2/l) sin (n∏x/l)

P= -ih(bar)d/dx

X=x

3. The attempt at a solution

All integrals are from 0 to L

I'm typing this on a playbook so I won't show all my steps.

-2ih/l ∫sin(n∏x/l)d/dx(xsin(nx/l)

Which I got to be : sinx(sinx) + xcosx. My teacher however never gave us the integral of xcosx from 0 to l. So how can I solve this?

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Expectation value of momentum times position particles in a box

**Physics Forums | Science Articles, Homework Help, Discussion**