Book excerpt: A physics course for 9th to 11th grade covering essential physics concepts. Introductory Physics is a mastery-oriented text specially designed to foster content mastery and retention when used with the companion resource materials available on CD from Centripetal Press. Another key feature of Centripetal Press texts is the integration of related subjects: history, mathematics, language skills, epistemology (the philosophy of knowledge) as well as frequent references from the humanities. Fresh pedagogical ideas and presentation make this text a superior choice for all learning environments where rigor and lucidity are desired in a text.