7.3 Universal Law of Gravity and Planetary Motion | General Physics

Chad revisits the topic of gravity in the context of planetary motion. He presents once again the universal equation for gravity but additionally shows a new equation for gravitational potential energy for situations not near the surface of the Earth. He then derives an equation for the escape speed (i.e. escape velocity) for a projectile off of a planet.

Chad then solves problems comparing and contrasting the weight of a man on the surface of the Earth vs in a high orbit above the Earth revealing what might be a surprising result for many. He then calculates the speed required for a satellite to maintain a stable circular orbit around the Earth at an altitude of 260km and the escape speed for a projectile from the Earth.

Chad concludes the lesson with a discussion of Kepler's Law of Planetary Motion. He describes all three of Kepler's laws and then calculates the period of orbit for the Earth using the equation given by Kepler's 3rd Law.

00:00 Lesson Introduction
00:51 Reviewing Universal Gravity and the Force of Gravity Formula
02:03 Universal Gravitational Potential Energy
04:01 Escape Speed (and Derivation of Escape Speed Formula)
09:04 Weight on Earth vs Weight in Orbit Gravity Problem
15:14 How to Calculate the Speed for a Stable Orbit Problem
18:29 How to Calculate Escape Speed Problem
20:16 Kepler's Laws of Planetary Motion
24:02 Kepler's Third Law Derivation
26:21 How to Calculate the Period of Orbit of a Planet Problem

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