Exercises: Coulomb's Law

Work through each section in order. Use $k = 9 \times 10^9$ N·m²/C² throughout. Show your work on all calculation problems.

Grade 11·20 problems·~35 min·OpenStax Physics (High School)·section·sec-18-2

Work through problems with immediate feedback

Fluency Practice

Use $k = 9 \times 10^9$ N·m²/C². Show your work and state the direction of each force.

Two protons are separated by a distance $r$ . Which of the following correctly describes the electric force between them?

Attractive, with magnitude $F = \frac{k e^2}{r^2}$

Repulsive, with magnitude $F = \frac{k e^2}{r^2}$

Attractive, with magnitude $F = \frac{k e}{r^2}$

Zero — protons are too small to exert detectable forces.