I went about calculating the pressure developed in a uniformly charged spherical shell like this
consider an infinitesimal area dA on the surface of the shell with a charge density of 's'.
Charge on the area is q=s*dA
from gauss law the electric field at the surface(perpendicular to the surface always)= s/eps0
force on the area= E*q=s^2*dA/eps0
pressure= F/dA=s^2/eps0

I think I am missing a factor of 1/2.

Can someone tell me the mistake?
Thanks a lot

Probably comes from double-counting the charges. Have you tried looking at this from an energy perspective? What is dV/dr, when V is the potential for a small charge on the sphere as a function of radius. -qdV/dR=force.