Why can't a particle in an energy eigenstate be moving classically?

[sheelbe999]

Homework Statement

I'm really struggling with this one guys, the question is:

Explain why a particle which is in an energy eigenstate cannot be moving in the
classical sense.

Homework Equations

I'm guessing the TISE and TDSE are relevant

The Attempt at a Solution

 

[gabbagabbahey]

"Moving in the Classical sense" means that the expectation value of the particle's speed is non-zero. So, try calculating that expectation value for a particle in an energy eigenstate...