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The radial stresses at the inner and at the outer surface is 0 psi since the traction is zero at a free surface.outer surfaces can be deduced from the boundary conditions:

• The radial stress at the outer surface is 0 psi since the traction is zero at a free surface.
• The radial stress at the inner surface is -1000 psi since it has to equal the applied normal traction (radial direction is also the normal direction here). The negative sign indicates that the applied traction is compressive. 

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