This book is part of our research on classical mechanics. According to our opinion a theory such as classical mechanics, with its long lifespan, has many challenges. The method of writing the book is totally informal and we have not used any other book, either in choosing discussions or in incorporating them in the book.Therefore, as evidenced by the end of the book, it is used more than the articles. In order to study this book and thinking on the results of its discussions, introductory mechanics and calculus and differential integrals (at least in the elementary level) are essential. In some chapters of the book, we have tried to put as much scope as possible into the philosophical debates of classical mechanics, especially in the principle of least action, comparing the attitudes of the old philosophers to very effective.