Gravity, The Basics (High School Physics)
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# Gravity, The Basics (High School Physics)

An introduction to Newtonian Gravitation (kinematics, forces, gravitational fields, circular motion, orbital motion)
5.0 (2 ratings)
23 students enrolled
Created by Edouard Reny
Last updated 6/2019
English
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This course includes
• 4.5 hours on-demand video
• Access on mobile and TV
• Certificate of Completion
Training 5 or more people?

What you'll learn
• Master the basics of Newtonian Gravity.
• Solve linear motion problems (with constant acceleration).
• Understand and apply Newton's Universal Law of Gravitation and realise how it is derived.
• Understand what is meant by the word "Field" when talking about electric fields, magnetic fields or gravitational fields.
• Understand and apply the concept of gravitational fields to questions and problems.
• Solve questions involving the gravitational field strength
• Apply 1st and 2nd laws of Newton to gravity (which leads to the equivalence principle).
• Use circular motion principles to solve problems in Physics.
• Apply gravitational field notions and circular motion concepts to handle orbital motion.
• Apply the third law of Kepler.
• Understand the motion of celestial objects (moons, planets, stars etc).
Requirements
• Basics in algebra (equivalent grade 9)
• Basics in vector mathematics (equivalent grade 9) - Operations on vectors are reminded briefly during the course.
Description

Welcome to the Course: “Gravity, The Basics”

*** What you will learn ***

“Gravity, The Basics” teaches the elementary notions you need to understand and apply Newtonian gravity:

_ Solving 1-dimensional motion problems (Linear Kinematics),

_ Newton’s Universal Law of Gravitation,

_ What are fields,

_ Gravitational fields and gravitational field strength,

_ Gravitational field lines,

_ Circular motion: angular velocity, centripetal acceleration and force, how to apply these notions to solve questions in physics,

_ Orbital motion and the third law of Kepler.

*** Who is this course for? ***

This course is suited for high school students studying Physics (from grade 10 to 12). The content of this course complies with Chapter 6 of the IB Physics Program and Topics 6.2 and 11 of the A-Level Curriculum.

It contains many exercises in all sections as well as exam inspired questions (especially section 6). This course is a very valuable tool for preparing any upcoming physics exam that may have questions related to gravity.

This course is also suited as a refresher for early university students that wish to solidify their understanding on Newtonian gravity.

And of course, any person interested in physics and in how the world works will also enjoy the voyage: I often invite my students on adventures beyond the academic…

*** Structure of the course ***

“Gravity, The Basics” is structured in 6 sections. All sections contain lessons, applied examples, exercises with detailed correction, fun science facts and anecdotes, and many tips and tricks on how to approach questions in Physics. The last section is a little different: it is composed of a general summary and the Gravity Quiz!

Section 1, “Linear Motion”, presents a step-by-step technique to solve all linear motion problems when the acceleration is constant. This class is not essential for this course, yet the resolution technique presented is an extra “weapon” for students in feeling confident when facing a physics problem that involves motion.
If you are familiar with linear motion, the SUVAT technique and are comfortable solving questions, you can skip this section. Otherwise, I recommend you view it and work on the exercises: it is truly a good investment for your study of Physics in general. Note that this section can be taken independently from the course.

Section 2, “Newton’s Universal Law of Gravitation” is usually the first notion about gravity that is taught to students. If you are familiar with this, and can solve direct application questions, you can also skip this section. If not, I strongly recommend you go through this section and the exercises before moving forward with the course: Indeed, this section can be seen as the doorway to the deeper dive that follows.

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

Section 4: “Circular Motion” prepares 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). As for section 1, the information provided in this section applies to many other areas of Physics (mechanics, electricity, magnetism, atomic, nuclear and particle physics).
Please note that section 4 can also be taken independently from the course.

Section 5, “Orbital Motion” discusses the motion of bodies in circular orbits around a massive object: This section blends notions taught in section 3 (gravitational fields) with notions presented in section 4 (circular motion). It also discusses the 3rd law of Kepler, so useful for astronomers!

Section 6: “Wrapping-up and Gravity Quiz”. You have viewed all 5 sections, and worked on the exercises? Then, it is 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.

*** Teaching style ***

My name is Edouard Reny, by training, I am a PhD in Solid State Chemistry and an engineer in Material Sciences. I have taught at university during my academic years. After this, during my industrial years, I have trained chemical engineers in electrochemical analytical techniques.

Since 2013, I am an independent teacher in Physics. I have supported about 5 dozen IB Physics, A-Level and AP students, one-on-one or in small groups. And, for now, 100% have passed their Physics exam!

The physics curricula that are taught today in high schools are truly fascinating, much more than 30 years ago when I myself was a high school student. Still, I do observe a problem… I see it during the first sessions with a new student: a lack of enthusiasm and no fascination whatsoever for the marvels they are being shown… For high school students, Physics appears just like another painful topic to handle…

After a few months with me, the students start to feel the fascination, and get inspired by it. Many of my students, that took a tutor (me) just to help them pass this “horrible” topic, got high marks at exams. And guess what, a large fraction of these are now graduating in an area of Physics at University! They got hooked!

My teaching style is focused on inspiring students, because when you are hooked, study becomes a hobby, and when an activity becomes a hobby, it becomes also painless to get good at it: Consequence: the marks go up significantly.

So expect me using equations yes, and a lot of them, as tools to discuss their true meaning. These equations will allow us to travel and observe the diamonds of our cosmos: For example, in this course we will embark for a voyage towards the underground oceans of Enceladus (a moon of Saturn), above the steaming volcanoes of Io (a moon of Jupiter), within the icy worlds of the Kuiper Belt at the edge of the Solar System, and even nearby an exploding star.

This is how I teach Physics, by making you fascinated by the marvels of our Universe.

*** What does this course NOT contain – and potential future developments ***

This course focuses on the basic notions of gravitation only, and follows standard level high school curricula. It does not introduce more advanced notions like gravitational potential energy or gravitational potentials, which can be taught in the higher levels of some of these curricula.

The course also remains within the boundaries of Newtonian Gravity: It does not mention nor describe any notions relative to Einstein’s General Relativity.

This course was a lot of work to put together (around 200-300 hours): if it meets success and upon request of students, I will consider developing a similar course format for Gravitational Potentials (“Gravity, Advanced”) and eventually a course for General Relativity. If I do this, these will also conform with High School curricula.

*** Enjoy the Voyage! ***

Now, it’s time to tighten your seat-belt, and let’s get started!

Who this course is for:
• High school students taking Physics.
• High school students preparing their exams in Physics (IB, A-Levels etc...).
• Entry university students that need a 'refresher' in the basics of Newtonian Gravity.
• Any person that is interested in the Physics of Newtonian gravity.
• High School Physics Teachers that are looking for inspiration to teach their own classes on the subject.
Course content
Expand all 50 lectures 04:35:16
+ Linear Motion
5 lectures 31:10

Welcome to the Introduction Video of the Linear Motion section of "Gravity The Basics"

Before we start diving into Gravity, let’s learn how to solve Linear Motion questions promptly and without any pain! This section will be useful to you in many areas of Physics, not only for this course!

This Section will teach you the SUVAT method to solve questions in Linear Motion (AKA Kinematics).

Motion is a subject that appears in all areas of physics where you need to be able to predict the path of a body when it is subjected to a constant force (thus a constant acceleration).

This section will show you in five clearly defined steps how to figure this out when the motion is in 1 dimension. It comes with many exercises for you to train on. With a little practice, you should soon become a master at solving motion questions! Actually, with even further practice, you can even start solving problems mentally!

Content of the section:

Video 1: The lesson itself presenting the SUVAT method and exemplifying it on practical examples.

Video 2: A mathematical proof of the motion equations which are used. Not absolutely necessary to handle the questions, but a great way to review your algebra.

Video 3 + Video 4: 4 exercises for you to work on, all followed by detailed correction and explanations.

Exercises are provided also in pdfs under two forms: Full Picture and Printable. The latter allows you to work on the exercises away from your computer. Answers are provided too in a pdf document.

Preview 01:24

Motion is a subject that appears in all areas of physics where you need to be able to predict the path of a body when it is subjected to a constant force (thus a constant acceleration).

This video shows you in five clearly defined steps how to figure out any 1D motion question.

A summary of the technique is attached. You can use it as a cheat sheet!

Step by step technique to solve Linear Motion problems
12:09

In the previous video, we used 4 motion equations which allow solving any motion problem with constant acceleration. But where do they come from?

This lecture is a mathematical proof of the motion equations which are used.  Although viewing this video is not absolutely necessary for the rest of the course, understanding where fundamental equations come from helps building confidence, and besides, it is a great way to review your algebra!

Deriving Motion Equations
05:30

This video present 2 basic training exercises to familiarize yourself in solving Linear Motion questions.

When an exercise appears on the screen, pause the video, and try to figure it out. Then resume the video for a detailed correction. If you missed something in Lecture 2 that presents the technique to solve these questions, do not worry. the solution proposed are quite detailed!

You can also carry out the exercises away from the computer by downloading and printing the attached pdf files. These files contain the texts of all exercises in this section as well as their their answers (For a detailed correction, you have to watch the video.).

Linear Motion Exercises 1 & 2
05:38

This video present 2 more training exercises to familiarize yourself in solving Linear Motion questions.

When an exercise appears on the screen, pause the video, and try to figure it out. Then resume the video for a detailed correction. If you missed something in Lecture 2 that presents the technique to solve these questions, do not worry. the solution proposed are quite detailed!

You can also carry out the exercises away from the computer by downloading and printing the attached pdf files. These files contain the texts of all exercises in this section as well as their their answers (For a detailed correction, you have to watch the video.).

Linear Motion Exercises 3 & 4
06:29
+ Newton's Universal Law of Gravitation
4 lectures 28:24

This video is the introduction to the section of the course dedicated to Newton’s Universal Law of Gravitation!

Sir Isaac Newton was a real genius, he realized that the force that makes an apple fall is of the same nature than the one that makes planets turn! This was a slick thought for the 17nth century!

This section will present his insight and the formula that came out of it. Then, it will be your turn to be active by solving 4 exercises. In all cases, you can enjoy a detailed correction of these exercises, spiced with fascinating physical facts that rise from the Universal Law of Gravitation.

*** Content of this section ***

Video 1: The lesson itself presenting the Universal Law of Gravitation.

Video 2: Two exercises with their corrections.

Video 3: Two more exercises with their corrections.

The text of the exercises and the answers are provided as printable pdf files. For detailed corrections, you need to view the videos

*** Level of this section***

This section is suited for end high school (from grade 10 to 12) and entry level University students taking Physics. Any person interested in Physics and in need of a refresher on the Universal Law of Gravitation will also enjoy this section.

Preview 01:28

This video presents Newton’s Universal Law of Gravitation. It starts by retracing how Newton probably came up with the idea of an attraction force between objects.

Then the law is explained in detailed, followed by a solved example.

Newton’s Universal Law of Gravitation – The lesson
09:09

This video present 2 basic training exercises to familiarize yourself with Newton’s Universal Law of Gravitation.

When an exercise appears on the screen, pause the video, and try to figure it out. Then resume the video for a detailed correction.

You can also carry out the exercises away from the computer by downloading and printing the attached pdf files. These files contain the texts of all exercises in this section as well as their answers (For a detailed correction, you have to watch the video).

Training Exercises 1 & 2 (Universal Law of Gravitation)
06:53

This video present two more training exercises to familiarize yourself with Newton’s Universal Law of Gravitation. These are just a little less easy than in the previous video (2 stars out of 4 instead of 1)

When an exercise appears on the screen, pause the video, and try to figure it out. Then resume the video for a detailed correction.

You can also carry out the exercises away from the computer by downloading and printing the attached pdf files. These files contain the texts of all exercises in this section as well as their answers (For a detailed correction, you have to watch the video.).

Training Exercises 3 & 4 (Universal Law of Gravitation)
10:54
+ Gravitational Fields
9 lectures 01:18:18

This video introduces the content of this section, at the heart of Newtonian gravity, gravitational fields.

The videos in this section present all the basics you need to gain a good understanding of gravitational fields.

*** Section summary ****

When you hear the words gravitational field, do you know what is meant by the word field?

This will be made very clear in the first video. You’ll see how this concept is actually really simple. After you’ve understood what a field is, we’ll dive deep in gravitational fields.

First, we describe the quantity associated with every point of gravitational field, the gravitational field strength. This will be followed by series of exercises aimed at making you comfortable with this notion.

In the following lesson, we blend in some vector mathematics: yes, the gravitational strength is a vector quantity. It also has a direction. Again, many exercises will be proposed to train your new knowledge.

And finally, in the last video, we discuss a way to represent a gravitational field as a whole using the concept of field lines.

*** Content ***

Video 3.0: Introduction.

Video 3.1: What is a Field?

Video 3.2: Gravitational Fields.

Video 3.3 and 3.4: Exercises related to Video 3.2.

Video 3.5: Gravitational Fields are Vector Fields.

Video 3.6 and 3.7: Exercises related to Video 3.5.

Video 3.8: Gravitational Field Lines (Radial Fields, Fields created by 2 masses, Uniform Fields.)

The text of the exercises and the answers are provided as printable pdf files. For detailed corrections, you need to view the videos

*** Level of this section***

This section is suited for end high school (grade 11 and 12) and entry level University students taking Physics. Any person interested in physics and wishing to finally grasp the concept of gravitational field will also enjoy the voyage.

Preview 03:08

When you hear the words "Electric Field, "Magnetic Field", or "Gravitational Field", do you know what is meant by the word "Field"?

This video is aimed at making you familiar with this notion. You will realize how simple it is: you actually use it everyday without even knowing it!

Once you have grasped what a field is we will be able to move on and explore gravitational fields.

What is a Field ?
03:58

This Video defines what a gravitational field is. It also presents the quantity associated with each point of a gravitational field: The gravitational field strength.

As an applied example to the lesson, an exercise is proposed at the end of the video: calculate the gravitational field strength at the surface of the Earth.

Gravitational Fields - Lesson Video
13:33

This video presents two exercises to get familiar with the notion of gravitational field strength:

Exercise 1: Determining how much the gravitational field strength changes after a star exploded and lost a fraction of its mass?

Exercise 2: Calculating the gravitational field strength at a given height above the clouds of Saturn.

When an exercise appears on the screen, pause the video, and try to figure it out. Then resume the video for a detailed correction.

You can also carry out the exercises away from the computer by downloading and printing the attached pdf files. These files contain the texts and answers of all exercises related to the lesson Video 3.2 (Lecture 12). For a detailed correction, you have to watch the video.

Training Exercises 1 & 2 (Gravitational Fields)
05:23

This video presents three more for you to realise how much can be done with this notion of gravitational field strength:

Exercise 3: Calculating the mass of a planet based on the gravitational force felt by an astronaut in orbit around it

Exercise 4: Calculating the gravitational effect of the black hole at the centre of our galaxy on our own star, The Sun.

Exercise 5: Playing with the units of the gravitational field strength quantity.

When an exercise appears on the screen, pause the video, and try to figure it out. Then resume the video for a detailed correction.

You can also carry out the exercises away from the computer by downloading and printing the attached pdf files. These files contain the texts and answers of all exercises related to the lesson Video 3.2 (Lecture 12). For a detailed correction, you have to watch the video.

Training Exercises 3, 4 & 5 (Gravitational Fields)
08:54

The gravitational strength is a vector quantity. It also has a direction. This video explores this concept by blending in some vector mathematics.

As application example, we determine the magnitude and direction of the gravitational field strength at a given point around a binary star.

Gravitational Fields are Vector Fields – Lesson Video
11:22

This video presents two exercises which will put into application the fact that a gravitational field strength is a vector quantity, and therefore all operations on it need to be vector operations.

Exercise 1: Determining the Gravitational field strength at different points of an axis that contains two masses.

Exercise 2: Determining the position between two masses where no gravitational force would be perceived by an object placed at that point. In other words, determining the position of a Lagrange point.

When an exercise appears on the screen, pause the video, and try to figure it out. Then resume the video for a detailed correction.

You can also carry out the exercises away from the computer by downloading and printing the attached pdf files. These files contain the texts and answers of all exercises related to the lesson Video 3.5 (Lecture 15). For a detailed correction, you have to watch the video.

Training Exercises 1 & 2 (G. Fields as Vector Fields)
10:06

This video presents two exercises which will put into application the fact that a gravitational field strength is a vector quantity, and therefore all operations on it need to be vector operations.

Exercise 3: The closes star from us is part of the Alpha Centaury stellar system, a ternary stellar system (containing 3 stars gravitationally bound). This exercise proposes to calculate the gravitational force exerted by two stars on the third one.

When an exercise appears on the screen, pause the video, and try to figure it out. Then resume the video for a detailed correction.

You can also carry out the exercises away from the computer by downloading and printing the attached pdf files. These files contain the texts and answers of all exercises related to the lesson Video 3.5 (Lecture 15). For a detailed correction, you have to watch the video.

Training Exercise 3 (G. Fields as Vector Fields)
11:17

This video explains what is a field line and how to draw it based on gravitational field strength vectors. It describes and explains how to build field lines occurring in radial fields, fields created by two masses and uniform fields.

Note that what is presented here is also valid for electric fields.

Gravitational Field Lines - Lesson Video
10:37
+ Circular Motion
9 lectures 42:49

This video starts with a presentation of the content in this section about Circular Motion: by viewing this section, you will gain an understanding of all the fundamentals related to circular motion. This knowledge will allow you to solve many problems in physics: Using the mathematical consequences of a motion which is circular allows to derive many useful relations between quantities, and in the end, easily solve problems that otherwise would appear very difficult.

After the short introduction, the videos answers to the question: What is an angle?

Videos 4.2 to 4.4 (lectures 20 to 22) discuss the various dynamic quantities to consider when dealing with a system in circular motion: angular velocity, centripetal acceleration and centripetal force respectively. Mathematical proofs of the relations between these quantities are also presented.

Video 4.5 (lecture 23) is an application example: Principles of circular motion are applied in order to determine the kinetic energy of an electron in orbit around a proton (i.e. a hydrogen atom).

In Video 4.6 through 4.9 (lectures 24 to 27), it is your turn: each video presents an exercise for you to work on, followed by a detailed correction on the board. Videos 4.6 (lecture 24) and 4.7 (Lecture 25) are straight forward applications of the formulas. Video 4.8 (Lecture 26) requires a little more reflection, and video 4.9 (lecture 27) is challenging.

***********************
Content of the class

***********************

Video 4.1: Introduction + Lesson - What is an angle?

Video 4.2: Lesson - Angular Velocity

Video 4.3: Lesson - Centripetal Acceleration

Video 4.4: Lesson - Centripetal Force

Video 4.5: Application example: The kinetic energy of the electron in a hydrogen atom

Video 4.6: Training Exercise 1 (Easy)

Video 4.7: Training Exercise 2 (Easy)

Video 4.8: Training Exercise 3 (moderate difficulty)

Video 4.9: Training Exercise 3 (challenging)

All 4 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.

***********************
Level of this section

***********************

This section is suited for end high school (grade 11 and 12) and entry level University students taking Physics. Any person interested in Physics and in need of a refresher about circular motion will also enjoy this section.

Preview 03:28

This video presents the concept of angular velocity. It also discusses the relation of angular velocity with linear velocity, period and frequency.

Angular Velocity
03:06

This video discusses in detail the concept of centripetal acceleration. We show that an acceleration that leads to a circular motion is always directed towards the center. We also prove the formula that links centripetal acceleration with linear velocity, angular velocity and radius of the circular motion.

Centripetal Acceleration
05:45

By applying Newton’s second law, we realise that a force creating a circular motion is also centripetal. We deduce from this the relation between centripetal force and other quantities such as the angular velocity, the linear velocity, the radius of the circular motion and the mass of the object in circular motion.

We conclude that such a formula is a mathematical expression of a centripetal force and that such a relationship is key in solving problems in Physics.

Centripetal Force
02:46

As an example of the solving power of circular motion principles, this video presents an application example: Calculating the kinetic energy of an electron orbiting a hydrogen atom.

Application Example
04:54

The exercise presented in this video is to familiarise the viewer with the basic formulas used in circular motion. It is a direct application of the relations presented in the lesson videos.

Difficulty: Easy

When the exercise appears on the screen, pause the video, and try to figure it out. Then resume the video for a detailed correction. You can also carry out the exercises away from the computer by downloading and printing the attached pdf files. These files contain the texts and answers of all exercises related to this section. For a detailed correction, you have to watch the video.

Exercise 1 (Circular Motion)
05:00

In this video, the exercise consists in calculating the linear and angular speed of the moon in orbit around the Earth. The correction goes even further by calculating the duration of a lunar cycle.

Difficulty: Easy

When the exercise appears on the screen, pause the video, and try to figure it out. Then resume the video for a detailed correction. You can also carry out the exercises away from the computer by downloading and printing the attached pdf files. These files contain the texts and answers of all exercises related to this section. For a detailed correction, you have to watch the video.

Exercise 2 (Circular Motion)
02:34

In this video, the exercise consists in determining the maximum speed for a car driving on a bridge without it loosing contact with the ground (The bridge is considered like the arc of a circle.

Difficulty: Moderate

When the exercise appears on the screen, pause the video, and try to figure it out. Then resume the video for a detailed correction. You can also carry out the exercises away from the computer by downloading and printing the attached pdf files. These files contain the texts and answers of all exercises related to this section. For a detailed correction, you have to watch the video.

Exercise 3 (Circular Motion)
06:03

The exercise in this video consists in determining algebraic expressions for linear and angular velocities of a ball hanging from a rope and for which the oscillation describes horizontal circles.

Difficulty: Challenging

When the exercise appears on the screen, pause the video, and try to figure it out. Then resume the video for a detailed correction. You can also carry out the exercises away from the computer by downloading and printing the attached pdf files. These files contain the texts and answers of all exercises related to this section. For a detailed correction, you have to watch the video.

Exercise 4 (Circular Motion)
09:13
+ Orbital Motion
9 lectures 39:49

By viewing this section, 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 sections 3 and 4 of this course).

This concept is detailed in the first video (video 5.1 – lecture 29) where you will learn what is an orbit and realize how the velocity of an orbiting object can define the height of this 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 (lecture 36) shows how to use the 3rd law of Kepler to design the motion of a bunch planets orbiting a star.

*** Content of the section ***

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.

*** Level of this Section ***

This section 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

Preview 01:48

The lessons start with a detailed explanation of what is meant by an ‘orbit’. It shows how a centripetal force applied to an object with linear velocity perpendicular to that force leads to a circular motion.

Then, we realize that the centripetal force is actually the gravitational force. This allows to derive a formula that links linear velocity of an object in orbital motion to the distance from the center of the mass it is in orbit around, and to its distance from it.

The video closes with an application example: calculating the orbital speed of the moon!

Orbital Motion (Lesson Video)
08:02

This exercise is a straight application of the formula derived in the lesson video about orbital motion:

It asks the student to calculate the linear and angular speeds of the Earth around the Sun, and then deduce the length of the Earth year in days.

Difficulty: Easy

When the exercise appears on the screen, pause the video, and try to figure it out. Then resume the video for a detailed correction. You can also carry out the exercises away from the computer by downloading and printing the pdf files attached to this video. These files contain the texts and answers of all orbital motion exercises. For a detailed correction, watch the video.

Exercise 1 (Orbital Motion)
04:56

Knowing the period of revolution of Io, a moon of Jupiter, and its distance from the center of Jupiter, the student is asked to determine the mass of Jupiter.

Difficulty: Moderate

When the exercise appears on the screen, pause the video, and try to figure it out. Then resume the video for a detailed correction. You can also carry out the exercises away from the computer by downloading and printing the pdf files attached to this video. These files contain the texts and answers of all orbital motion exercises. For a detailed correction, watch the video.

Exercise 2 (Orbital Motion)
03:51

This exercise is a little more complicated: It asks the viewer to derive from scratch that for a moon in circular orbit around a planet, the product of the square of its angular speed with the cube of the distance from the center of the planet is a constant. Then using this relation, the student is asked to determine various characteristics of the Saturnian system.

This exercise is a hidden disguise for making the student derive the third law of Kepler without even realizing it! A great introduction to the next video.

Difficulty: Difficult

When the exercise appears on the screen, pause the video, and try to figure it out. Then resume the video for a detailed correction. You can also carry out the exercises away from the computer by downloading and printing the pdf files attached to this video. These files contain the texts and answers of all orbital motion exercises. For a detailed correction, watch the video.

Exercise 3 (Orbital Motion)
08:47

Combining equations of circular motion with those of orbital motion leads to an interesting result: the ratio of the cube of the radius of the circular orbit to the square of the period of the orbit is a constant. This relation is called the third law of Kepler.

In this video, we derive such relation and then exemplify its application by calculating the length of the year on Mercury.

Preview 05:25

This exercise asks the student to determine at what  height an artificial satellite must be located to remain geostationary. This question is a typical application of the third law of Kepler.

Difficulty: Easy

When the exercise appears on the screen, pause the video, and try to figure it out. Then resume the video for a detailed correction. You can also carry out the exercises away from the computer by downloading and printing the pdf files attached to this video. These files contain the texts and answers of all exercises related to Kepler’s 3rd Law. For a detailed correction, watch the video.

Exercise 1 (Kepler’s 3rd Law)
03:04

In this video, the student is invited beyond Neptune, to the edge of our solar system, in the Kuiper Belt. She/He will be visiting to Haumea, a dwarf planet, discovered in 2004 deep inside the Kuiper Belt. In the Video, the Student is asked to calculate in what year Haumea will appear again in the same position it was originally discovered.

Difficulty: Moderate

When the exercise appears on the screen, pause the video, and try to figure it out. Then resume the video for a detailed correction. You can also carry out the exercises away from the computer by downloading and printing the pdf files attached to this video. These files contain the texts and answers of all exercises related to Kepler’s 3rd Law. For a detailed correction, watch the video.

Exercise 2 (Kepler’s 3rd Law)
02:45

You may have noticed in various videos of this course, an animation with three planets in orbit around a star.

The motion of the planets in the animation actually obey the 3rd Law of Kepler.

In this video, I show how to apply the 3rd Law of Kepler to an animation!

Creating a graphic animation using Kepler’s 3rd Law (Bonus Video)
01:11
+ The Gravity Quiz
14 lectures 54:46

In the previous sections, you have learned about the basics of Newtonian gravity: Gravitational Forces, Gravitational Fields, Circular Motion, Orbital Motion etc…

Now it is time to check your new knowledge with a Quiz!

The selection of questions I wrote for this quiz mimics real exam questions you could encounter during a high-school final exam, such as IB or A-Levels exam. So, this section is also a great tool for high school students to test their knowledge! It is also a fun way to train the brain of anybody interested in this subject.

Before the quiz, I produced a ‘Wrap-up’ video that summarizes in just a few minutes the fundamentals we have discussed during the full course. Take the time to review it and if you do not understand or have forgotten something, go back to the relevant section.

The second video contains instructions on how to take this quiz so that the results remain meaningful to you in evaluating where you are at concerning the basics of Newtonian gravity. You can take the quiz in two different ways:

1st way: each video presents the question with a timer, and a detailed correction once the time is up. You can take the test question by question and get the answer immediately after each question.

2nd way (recommended): Download and print the pdf file that contains all 12 questions, and take the test far from any distraction and with a time limit: if you wish to feel the time pressure of a real exam, the time limit should be set at 18 minutes. If you wish to transform this quiz into a more enjoyable experience, or use it as a revision tool, set it to 25 minutes, or even 30 minutes.

Please note that these questions are typical of what you could find in an IB Physics (SL) or A-Level exam. 18 minutes would be the official time give to answer 12 questions.

All solutions are presented in detail in the videos, with sometimes a discussion that explores alternate solutions or ways to approach the problem. You can also find all solutions for a quick answer check by downloading the answer sheet (pdf file).

Have Fun and Good Luck!

************* Content of this section *************

Video 6.1: Wrapping Up!

Video 6.2: Instructions on how to take the Gravity Quiz

Video 6.3: Question 1

Video 6.4: Question 2

Video 6.14: Question 12

*** Level of this Section ***

This section is suited for end high school and entry level University students taking Physics. It is a great section for students to prepare themselves for final exams.

Preview 03:44

This video Presents two ways on how to take the quiz in order to get a good evaluation of where you are at regarding your knowledge of Newtonian Gravity.

The first way, is for the students that wish to continue learning while taking the Quiz: It consists in taking the quiz linearly, question by question with a detailed correction after each question.

The second way is typical of official exams like the IB Physics SL, and A-Level Physics. It is suited for high school students preparing their exams. Download and print the pdf file that contains all 12 questions, and take the test far from any distraction and with a time limit: if you wish to feel the time pressure of a real exam, the time limit should be set at 18 minutes (time given for 12 question in official exams, like the IB or the A-Levels). If you wish to transform this quiz into a more enjoyable experience, or use it as a revision tool, set it to 25 minutes, or even 30 minutes

Preview 02:05

The Gravity Quiz - Question 1

The printed version and the answers are attached to lecture 38 (second video of this section)

Question1
07:36

The Gravity Quiz - Question 2

The printed version and the answers are attached to lecture 38 (second video of this section)

Question 2
02:58

The Gravity Quiz - Question 3

The printed version and the answers are attached to lecture 38 (second video of this section)

Question 3
01:57

The Gravity Quiz - Question 4

The printed version and the answers are attached to lecture 38 (second video of this section)

Question 4
05:45

The Gravity Quiz - Question 5

The printed version and the answers are attached to lecture 38 (second video of this section)

Question 5
03:50

The Gravity Quiz - Question 6

The printed version and the answers are attached to lecture 38 (second video of this section)

Question 6
03:27

The Gravity Quiz - Question 7

The printed version and the answers are attached to lecture 38 (second video of this section)

Question 7
02:59

The Gravity Quiz - Question 8

The printed version and the answers are attached to lecture 38 (second video of this section)

Question 8
03:30

The Gravity Quiz - Question 9

The printed version and the answers are attached to lecture 38 (second video of this section)

Question 9
04:34

The Gravity Quiz - Question 10

The printed version and the answers are attached to lecture 38 (second video of this section)

Question 10
03:45

The Gravity Quiz - Question 11

The printed version and the answers are attached to lecture 38 (second video of this section)

Question 11
03:39

The Gravity Quiz - Question 12

The printed version and the answers are attached to lecture 38 (second video of this section)

Question 12
04:57