In order to discuss mechanical interactions, we need to understand forces and motion. In physical science, we can make use of all three of Newton’s laws of motion in a variety of situations. Energy analysis encompasses all areas of physics. In mechanics, energy analysis is all about potential and kinetic energy and their changes. In some of the experiments in this chapter, the gravitational potential energy is transformed to kinetic energy, and some of the energy is converted to another form by frictional forces. Teacher background information, assessment, safety notes, references, additional resources, and a keyword glossary are provided. This book selection also includes the Table of Contents, Preface, Acknowledgments, About the Authors, An Introduction to Phenomenon-based Learning, Appendix, Credits, and Index.