AP® Physics 1 & 2

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Comparing Electric Force and Gravitational Force


When calculating the net force on a planet to calculate its orbital motion, one can ignore the electrostatic forces on the planet and focus entirely on the gravitational forces.

On the planetary scale, why are electrostatic forces negligible compared to gravitational forces?


Because planets don’t have any protons or electrons in them.


Because the constant, k, in Coulomb’s law has a smaller magnitude than the constant, G, in Newton’s Law.


Because the range of the electrostatic force is limited to the size of an atom.


Because the planets are electrically neutral, containing equal numbers of protons and electrons.