Practice question

**Electrostatic force** described by F = (1/4π ε₀)·q₁q₂/r² obeys Newton's third law. Magnitude depends on q₁q₂ and 1/r², enabling quantitative estimation at given separation, with sign indicating attraction or repulsion. Force between +q and +q : F = (k q²/(3)²) = (k q²/9) (repulsive). Force between +q and -q : F = (k q²/9) (attractive). Angle between forces is 60°. Resultant: Fₙₑt = √(F² + F² + 2F² cos 60°) = √(3) F = (√(3) k q²/9) . Substituting values gives (√(3) k q²/9), which matches expected magnitude for this electrostatic configuration, confirming Coulomb's and Gauss's principles and charge quantization consistency.