The Physics
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Opus in profectus

Coulomb's Law

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Summary

F = k  q1q2  
r2
where…
ke =  8.99 × 109 N m2/C2
is the electrostatic constant
F =  1   q1q2  
4πε0 r2
where…
ε0 =  8.85 × 10−12 C2/N m2
is the vacuum permittivity