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Reviewed CSCA Physics question · Standard

Two point charges, +2 μC and +8 μC, are separated by 0.3 m in vacuum. What is the magnitude of the electrostatic force between them? (Use k = 9 × 10^9 N·m^2/C^2)

  1. 0.16 N
  2. 0.48 N
  3. 1.6 N
  4. 4.8 N
Show the answer and explanation

Correct answer

C. 1.6 N

Principle or equation

Coulomb's law: F = k |q1 q2| / r^2.

Why this answer is correct

F = 9e9 * (2e-6 * 8e-6) / (0.3)^2 = 9e9 * 16e-12 / 0.09 = 144e-3 / 0.09 = 1.6 N.

Example

Two 1 μC charges 0.1 m apart exert 0.9 N.

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