How to Calculate the Force Holding Two Halves of a Charged Sphere?

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To calculate the force holding two halves of a charged sphere together, one can use Coulomb's law, which is expressed as F = (1/4πε₀) * (q₁q₂/r²). The discussion suggests exploring alternative methods, such as computing the electromagnetic stress tensor derived from the field strength. Integrating this tensor over a strategically chosen surface may provide a simpler solution than traditional calculus methods. Participants are encouraged to share their experiences or insights regarding these approaches. The conversation emphasizes finding efficient calculation methods for this physics problem.
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Homework Statement


A metal sphere of radius R and total charge Q is cut into two equal halves. Find the force that is
necessary to hold the two parts together.

Homework Equations


##F = \frac{1}{4\pi \epsilon _0} \cdot \frac {q_1 q_2}{r^2}##
##\oint \vec E \cdot d \vec A = \frac{q}{\epsilon _0}##

The Attempt at a Solution


Is there any other way which is easy to calculate rather than columb's law (using calculus)?
 
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Have you tried computing the electromagnetic stress tensor from the field strength and integrating it over a "well chosen" surface?
 
The book claims the answer is that all the magnitudes are the same because "the gravitational force on the penguin is the same". I'm having trouble understanding this. I thought the buoyant force was equal to the weight of the fluid displaced. Weight depends on mass which depends on density. Therefore, due to the differing densities the buoyant force will be different in each case? Is this incorrect?

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