Why are the radial and the axial stress in a rotating thin ring null?

[Amaelle]

Homework Statement

look at the image

Relevant Equations

centrifugal forces

Greetings, while studying the stress in the rotating thing ring

and find out the last equation that says

I would like to understand why?
Thank you!

 

[Chestermiller]

The radial and axial stresses acting on the surface of the ring are just the compressional stress from atmospheric pressure. Since the ring is very thin, these persist throughout the thickness of the ring.

 

[Amaelle]

The radial and axial stresses acting on the surface of the ring are just the compressional stress from atmospheric pressure. Since the ring is very thin, these persist throughout the thickness of the ring.

thanks a million!