Two point charges of 1 microcoulomb and 1 microcoulomb are 0.3 m apart in vacuum. What is the force between them? (k = 9 x 10^9 N m^2 / C^2)
Answer and explanation
Correct answer: B. 0.1 N
- Step 1: Coulomb's law: F = k q1 q2 / r^2.
- Step 2: F = 9e9 x 1e-6 x 1e-6 / 0.3^2 = 0.1 N.
Answer
0.1 N.
Why not the others: The distance must be squared and the charges converted from microcoulombs; the other values slip on a power of ten or on the exponent.
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