Introduction to Physics-1

The work of a curious fellow

The beginning...

Hello. My name is J. D. Jones . To find out more about me and my background just click on my name which should appear underlined and in a distinct color. That underlined and colored name is an example of a "link". I will use links throughout this on line textbook to let you jump to new topics. I assume that since you have arrived at this page you are somewhat familiar with navigating around web sites so I will not spend more time on that subject. If you need additional help, use the Help menu item on your browser. Some of the images you find scattered around this page are screen shots from the lessons that follow. Others evidently are not. Just pause your cursor over any image to see a description.

The Java War

Those of us who write online material including Java applets, and those of you who need to run those applets are caught in the crossfire of the Java war. Microsoft tried to take over the Java virtual machine business a few years ago and failed. Sun Microsystems, the original Java company, won that battle and Microsoft is giving up, abandoning their Java technology and their support for Java. All new computers will now be shipped with the Sun Java runtime environment(JRE). That means that when websites are updated, the authors must make a choice about whether or not to move up to the modern Java language, not constrained by the limitations of the Microsoft virtual machine. At M. Casco we decided to move on, since the move will be have to be made sooner or later. Consequently if you have a computer shipped before 2004, you will probably need to download a free Java plugin from Sun and install it on your computer in order to use the applets included on this website. We apologize for any inconvenience. It seems that this is one of the prices we have to pay as customers for progress in the technology marketplace.

This is probably a good place to talk a bit about the organization of this course and some of the symbols you will see. There is a main thread to this story which is carried by the series of pages of which this is the first. These pages are linked together so that when you are at the end of one you may click on "Next" to go to the next one or on "Previous" to go back to the previous one. You may also click on a link to "Other" which gives you access to the course outline from where you may jump to any page. The links within the main thread are marked by a green ball like this.
main threadNext
Because there are people of various backgrounds taking this course, I may provide additional background material to fill in some of the details that you might need. The links to the underlying details will look like this example.
Background Material
Numbers, Functions and Graphs

When new terms are introduced, they will be linked to a glossary entry so if you find underlined and highlighted words in the text, just click on them to get to the definition. At the end of each page will be a link like this to jump to the glossary so you can browse for any term in which you are interested.

Gaussian second 

dot product in 


Some things are easier to understand than others. Probably we will not always agree on what the hard stuff is but I may mark things that I found confusing when I was learning, with a little devil like this to alert you to trouble.
devilish hard
You might want to take extra time going over that section.
Occasionally I will include a link to my email box that looks like this to make it easy for you to leave questions for me.
Are there any questions?

This email interaction is an important benefit of this online textbook over a printed book.
From time to time I may have a tidbit of information which some folks might find interesting but which is not required to understand the material. I will use a symbol like this to indicate a link to that stuff.
extra stuff

I am here as your coach and trainer as you try to become the modern day equivalent of the ancient wizards, a person who understands more than most about how the universe works. If you succeed, people will be coming to you for answers and depending on your advice. It is not magic but a deeper understanding from which you will draw your powers.
your new hat
You will be well paid for your services but the real payoff is the satisfaction that comes from understanding things. I am looking forward to working with you. As you read the material I have written and as we interact by email, we will come to know each other better.

We are beginning a long journey together but I will only go part way with you. If I am successful as your coach, you will go on to heights that I cannot reach. Imagine for example Joe Paterno tackling a running back or Bela Karoli doing a tumbling pass in a floor exercise to see what I mean. My job is to work with you to help you in two ways. One of my goals is to teach you some fundamentals. In particular, to teach you some physics which is the foundation of many sciences. The other goal is to teach you how to learn. You would not be at this level in your education if you had not already demonstrated a capacity to learn. What we are talking about here is getting to another level of learning.


ball toss

Many of you will be using this coaching program at the same time you are taking a formal course in physics at college or perhaps even at high school. You will have a teacher and textbook which will give you much of the information you will need. It is not my intention to replace either the teacher or the book. I am available through this on line course to provide extra examples, a different point of view, some additional help where you need it and most of all encouragement that it is all worth it. For those of you who are not taking a physics course along with this coaching program I will try to provide enough detail so that you will be able to make sense of the subject as a stand-alone course. If this was easy, everybody would be doing it and its value would be low. You have wisely chosen the high effort/high reward path.

Perhaps the ideal use for a course like this if you are a student is to give you a competitive advantage over the other people against whom you will be measured. Whether we like it or not there is an element of competition in everything we do. Striking the right balance between cooperation and competition is a life skill that really successful people have mastered. If you can work through this material with me, I guarantee that you will do well in that freshman physics course which many institutions use to cut the numbers of people in their advanced science and engineering courses to a select few. Not only that but your classmates are going to be looking to you for help. Never pass up an opportunity to teach. It is not until you have to explain something to someone else that you really learn it. Your academic reputation is going to be established in those first few semesters and success breeds success.

One of the secrets of successful learning is to get past the "Why do I have to know this?" issue. It is surprising how many otherwise very bright people will sabotage themselves by stewing about the payback for their learning effort rather than focusing on the material.
We need to spend time fooling around with frictionless pulleys, weightless rods and other stuff made from the rare element, unobtainium, in order to get on with the business of predicting the future. That is the work of scientists and engineers and that is where we are going with this learning adventure. I know that we will need frequent booster shots to immunize ourselves from this "What is the use of it all?" question so I will try to provide reminders of where we are going from time to time.

Everything has a beginning and the beginning for this journey is with a topic from physics called "Mechanics". Now here is an instance of where the language gets in the way. The word mechanics brings to mind people in matching pants and shirts with a name over the pocket and a box of tools.
one of the other mechanics
That is not the kind of mechanics we are talking about here. Physics, and all branches of science, must use words to convey information. The words used in the sciences come from the common language and have precise meanings, usually related to the common usage. Mechanics is the study of moving objects. For now we will deal with classical mechanics which deals with objects moving slowly relative to the velocity of light and objects large relative to the size of atoms and molecules. The reason for starting with mechanics is that many of the basic principles we will learn there apply to other topics.

There is another aspect of the language of science which we are going to have to come to grips with. That is mathematics. We are going to assume for the most part that you took and understood the college prep high school math courses. I know that for some of you that assumption is wrong and for some of you the assumption is OK but it was decades ago. So here's the deal. I will include a review of some mathematics in the background material as we go along. In fact here is the first of the promised background pages. There we will review the ideas of numbers, functions and graphs, and cover the symbols we will use for the mathematical operations of addition, subtraction, multiplication, division and exponentiation . I also introduce the graph paper that will serve as the drawing area for many future displays.
Do not be afraid to use the
Are there any questions?

link to fill in the gaps. In addition, we will be using the capability of the personal computer to avoid a lot of the mathematical complications.

Back in the 17th century, Isaac Newton and some of his friends (and enemies) invented calculus to replace millions of trivial calculations with a few complex ones. In the 21st century we have a tool to reverse that. What computers do best is simple math very fast. We will be substituting millions of simple calculations, easily understood, for the few complex ones. Oh, you will still need to learn calculus, but not very much for this course.

So let's get on with it.

two particle 

center of mass
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