This book grew out of notes from physics lessons for the liceo scientifico (Italian science-focused secondary school): each chapter is a narrative reconstruction of how a result is arrived at, with the pace of a lesson delivered aloud in class. Before getting into the physics itself, this guide explains the philosophy of the text, the typographic and notational conventions, how to move between the parts, how to set up the solution to a problem, and where to find the quick reference. It reads best with a pencil in hand: physics is only understood by doing it.