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## Homework Statement

There is a total of ##Q## charge on soap bubble of radius ##R##. What force is acting on one hemisphere by the other ?

## Homework Equations

Electrostatic pressure is ##P_e = 2\pi \sigma^2## for a spherical shell.

## The Attempt at a Solution

##P_e = F/A##

therefore ##F = AP_e = 2{A\over 2}\pi\sigma^2 = A \pi {Q^2 \over A^2} = {\pi Q^2 \over A} = {\pi Q^2 \over 4 \pi R^2} = {Q^2 \over 4\pi} ##

Given answer is ##{Q^2 \over \color{red}{8}\pi}##.

Where did I go wrong ?