The purpose of this book is to bring to the student an understanding of the basic physics involved not only in traffic crash investigation and reconstruction but also in crimes or other incidents where the movement of objects or persons is involved. The range of topics included are those considered to be fundamental and which best serve the purposes of illustrating the methods and procedures vital as an introduction to physics. Essentials of the subject as related to vehicle motion are stressed. The mathematics used is kept simple and in straightforward, easy-to-understand language. Comments and examples and a very comprehensive list of terms and definitions, supported by many illustrations and diagrams, are provided to give the reader a unified view of basic physics. All materials are prepared in both the English (U.S.) and metric (S.I.) systems. The text is intended to serve a need for investigators who possess a good knowledge and understanding of elementary algebra and trigonometry, and who have successfully completed at least an at-scene traffic crash investigation course and wish to further their knowledge towards competency in advanced traffic crash investigation and reconstruction.