the physicist

Volume I of the Ask the Physicist books

I am pleased to announce the publication of the first volume of a series of books based on Q&As originally published on the site. This first volume, From Newton to Einstein, Ask the physicist about mechanics and relativity, focuses on classical mechanics and relativity. Collected here are some of my favorite questions and answers, all organized with much added text to organize the material and tie it together. The book may be purchased online at Morgan & Claypool (publishers of the book), Amazon, or Barnes and Noble. A digital version for eReaders (epub format) is also available at Morgan & Claypool and a Nook version is available at Barnes and Noble; there is no Kindle version yet.


I am The Physicist! Since 2006 I have run a web site, www.AskThePhysicist.com, where I answer questions about physics. The site is not intended for answering highly technical questions; rather the purpose is to answer, with as little mathematics and formalism as possible, questions from intelligent and curious laypersons. For several years before my retirement from the University of Georgia I ran a similar Q&A site for the Department of Physics and Astronomy there. Over the last decade I have answered more than 4000 questions on line and uncounted more by brief email replies. I have found this very rewarding because it is an extension of my more than 40 years experience teaching and because I learn something new almost every day. The questions I receive reveal what aspects of physics interest people and what principles they do not grasp. They reveal a wide-spread thirst to understand how physics describes, on many levels, how our Universe works. It is gratifying that the site has on the order of 50–100 000 visits per month, far more than the number of questions asked; I interpret this to mean that there are many visits by people who simply like to read and learn.

This first book is about classical mechanics. Usually ‘classical’ calls to mind Newtonian mechanics and that is indeed where modern physics started. Since Newtonian mechanics provides the basis for so much of physics, it is logical that it should be the subject of the first book. Today, though, classical mechanics has come to include the theory of special relativity; after all, special relativity is the correct mechanics to which Newtonian mechanics is only an excellent approximation for most aspects of our everyday lives. The first section in each chapter of the book will consist of an overview of what I consider to be the bare-bones introduction to the material. To avoid having this read like a textbook, I mainly give the overview for one-dimensional situations, avoiding vector formalism which would at worst frighten away those with limited knowledge of physics or mathematics, or at best leave them yawning. I will fill in some gaps in the overview sections in the appendices; I will indicate when a specific appendix would be helpful in understanding the answer to a specific question.

So, if you, the reader are coming to this book with little or no physics knowledge, these overviews are for you; the overviews are what you absolutely must have to get anything from the book. And, since this is not a textbook and there is no way to include all the details and subtleties of physics, there will be the occasional question and answer which you will not really understand or which will require you to do a little research on your own. If you are coming to the book with prior physics knowledge, you might want to skip the overviews, although there is always the possibility that you could gain insight or benefit from reviewing the basics.

The bulk of the book is devoted to sections which will contain mainly categorized groups of Q&As from the web site, sort of a Best of Ask the Physicist. Enjoy and learn!



Author biography


1 Newtonian mechanics  

1.1 Overview  

1.1.1 Newton’s first law   

1.1.2 Newton’s second law   

1.1.3 Newton’s third law  

1.1.4 Linear momentum   

1.1.5 Energy   

1.1.6 This is all wrong!   

1.2 Newton’s laws misunderstood   

1.3 Air drag   

1.4 Gravity and Kepler’s laws   

1.5 Physics of everyday life   

1.6 Accelerated frames and fictitious forces  

1.7 Wagers, arguments and disagreements   

1.8 These are a few of my favorite things   

2 Special relativity   

2.1 Overview   

2.2 Newtonian mechanics is wrong   

2.3 Relativity of time, time dilation  

2.4 Relativity of length, length contraction   

2.5 The twin paradox  

2.6 How things look, how things are   

2.7 Linear momentum, force, energy   

2.8 The universal speed limit   

2.9 Energy from mass, mass from energy   

2.10 These are a few of my favorite things   

3 General relativity   

3.1 Overview   

3.2 Examples   

4 Wacky questions: sci-fi, super heroes, computer games, fantastic weapons, etc   

4.1 Wacky questions   

5 Epilogue   

5.1 Ask the psychic   

5.2 Off-the-wall hall of fame   


A Energy   

A1.1 Work-energy theorem in Newtonian mechanics   

A1.2 Potential energy   

A1.3 Energy in special relativity  

B Approximations in Kepler’s laws   

C Rotational physics   

D Centripetal acceleration  

E Friction  

F The constants of electricity and magnetism   

G Galilean and Lorentz transformations