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## Main Question or Discussion Point

It would be really appreciated if somebody could clarify something for me:

I know that stationary states are states of definite energy. But are all states of definite energy also stationary state?

This question occurred to me when I considered the free particle(plane wave, not a Gaussian packet). The time derivative of the mean value of the position is not constant in time but equal to hbar*k/m. But, plane waves are energy(and momentum) eigenstates for the free particle, that means that they are states of definite energy. So, what's the deal here?

Thanks!

I know that stationary states are states of definite energy. But are all states of definite energy also stationary state?

This question occurred to me when I considered the free particle(plane wave, not a Gaussian packet). The time derivative of the mean value of the position is not constant in time but equal to hbar*k/m. But, plane waves are energy(and momentum) eigenstates for the free particle, that means that they are states of definite energy. So, what's the deal here?

Thanks!

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