Orbital Motion - Physics - Gravity Course (Class 5)

Edouard RENY, Music Producer & Tutor in Physics

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9 Lessons (42m)
    • 1. Orbital Motion - Introduction

    • 2. Orbital Motion - Lesson (Video 5.1)

    • 3. The Speed of the Earth - Exercise (Video 5.2)

    • 4. The Mass of Jupiter - Exercise (Video 5.3)

    • 5. The Moons of Saturn - Exercise (Video 5.4)

    • 6. The 3rd Law of Kepler - Lesson (Video 5.5)

    • 7. Geostationary Orbits - Exercise (Video 5.6)

    • 8. A Visit to the Kuiper Belt - Exercise (Video 5.7)

    • 9. The 3rd Law of Kepler used in Animations - Application Example (Video 5.8)


About This Class

Have you ever wondered why the Moon, although attracted by the Earth, never falls on it? Instead, our Moon describes a circular path around it. How come? This class will make you understand why.

By taking this class, you will gain an understanding of Orbital Motion. Orbital Motion combines the laws of gravity with the principles of circular motion (We have reviewed respectively these topics in Classes 3 and 4 of this course). This concept is detailed in the first video (5.1) where you will learn what is an orbit and realise how the velocity of an orbiting object can define its orbit.

The three videos that follow are training exercises showing fun stuff you can do with orbital motion equations, like determining the speed of the Earth, calculating the mass of Jupiter or exploring the intricacies of the Saturnian system. This latter exercise will allow you to discover a celestial Law: The 3rd Law of Kepler that links the period of revolution of a body to the distance from the massive object it is orbiting around.

To exemplify this, we will fly far beyond Neptune, deep into the Kuiper belt, where dozens of mysterious draft planets live their frozen lives. We will also play closer to Earth, like calculating the height at which a TV satellite must be launched!

Finally, for those interested in animation, Video 5.8 shows how to use the 3rd law of Kepler to design the motion of a bunch planets orbiting a star.

*** Content of the class ***

Video 5.0: Introduction

Video 5.1: Lesson – Orbital Motion

Video 5.2: Training Exercise – The Speed of the Earth

Video 5.3: Training Exercise – The Mass of Jupiter

Video 5.4: Training Exercise – The Moons of Saturn

Video 5.5: Lesson – The 3rd Law of Kepler

Video 5.6: Training Exercise – Geostationary Orbits

Video 5.7: Training Exercise – A Visit to the Kuiper Belt

Video 5.8: Application Example – the 3rd Law of Kepler at the service of animation

All training exercises are provided as pdf files and formatted so that you can print the exercise and work on them away from the computer. Answers are provided also in a pdf document.


*** This class is part of a larger course named “Gravity, The Basics”. ***
“Gravity, The Basics” explores the elementary notions of Newtonian gravity.

Class 1: “Linear Motion” (because being comfortable with this notion will allow you to make the most of the full course). This class presents a step-by-step technique to solve all motion problems when the acceleration is constant. This class can be taken by itself.

Class 2: “Newton’s Universal Law of Gravitation”, which you can be seen as a doorway to the deeper dive we carry out in the next classes.

Class 3: “Gravitational Fields”, the core of this course: This class teaches first what is a field, and then dives into a deep description of gravitational fields, gravitational field strength and gravitational field lines. It is packed with many exercises aimed at making the student comfortable with these notions.

Class 4: “Circular Motion”, prepares you for the section on orbital motion. You are presented with a detailed explanation of fundamental quantities that occur in circular motion (angles, angular velocity, centripetal acceleration and forces). This class can be taken by itself.

Class 5: “Orbital Motion”, for you to master the motion of bodies in circular orbits around a massive object: This class blends notions taught in class 3 (gravitational fields) with notions presented in class 4 (circular motion), in order to get a good grasp of what is an orbit, and how to manipulate easily orbital motion concepts.

Class 6: “Wrapping-up and Gravity Quiz”. Once you have viewed all 5 classes, it’s time for the exam! After a 5-minute summary of all notions presented in “Gravity, The Basics”, 12 exam-like questions are presented and corrected in detail.


*** Level of this class ***

This class is suited for end high school and entry level University students taking Physics. Any person interested in Physics and in need of a refresher about orbital motion and gravity will also enjoy this class.