Question
Explain why we only need to concern ourselves with gravitational force to describe the orbit of the Earth around the Sun.
Final Answer
Please see the solution video.
Solution video
OpenStax College Physics for AP® Courses, Chapter 33, Problem 2 (Test Prep for AP® Courses)
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Video Transcript
This is College Physics Answers with Shaun Dychko. We need to explain why we only have to concern ourselves with gravitational force to describe the orbit of the Earth around the Sun? Well the Earth and the Sun are separated by a very, very large distance and the strong nuclear force acts only on a very small distance scale like the size of a nucleus and so this is much, much greater than that scale and so this strong nuclear force won't apply and neither does the weak nuclear force for the same reason. The electromagnetic force does work over very large distances but it requires a net charge on the objects and so the Earth would have to be positively charged while the Sun was negatively charged in order for their to be attraction due to the electromagnetic force and that's not the case so scratch that one off leaving us only with gravity so by process of elimination, we can say gravity must be responsible for the force to cause the Earth to orbit around the Sun. And then furthermore, we know that the presence of mass causes gravity so that's another reason why gravity is the only force causing the Earth to orbit the Sun.