A spherical shell of radius  R=1.5 cm has a charge q=20μC  uniformly distributed over it. The force exerted by one half over the other half is

Electrostatic PressureP=σ22∈0Force(F)=PA=PπR2                                         =σ22∈0πR2                                  σ=QA=Q4πR2 =Q216π2R4πR22∈0 F=Q232π∈0R2 =20×10−62×9×1098×1.5×10−22 =2000 N