Researchers and practitioners alike express concerns about the conceptual difficulties associated with the concepts of momentum and kinetic energy currently taught in school physics. This article presents an in-depth analysis of the treatment given to them in 44 published textbooks written for UK secondary school certificate courses. This is set against some of the more contentious issues apparent in the literature concerned with the underlying physics and pedagogical arguments about how best to help students understand. The research evolved a set of criteria which were used to scrutinize how texts explain ideas and exemplify their applications. Despite the evident merits of many textbooks, the findings suggest that incomplete explanations are surprisingly prevalent, with several fundamental issues likely to be unclear to student readers, particularly those relating to when and where conservation might apply. Confusion exists between these difficult and somewhat overlapping ideas, arguably through the neglect of constructivist considerations. The commonly emphasized mechanistic, number-crunching approach to the analysis of simple collision problems is judged to be un-profitable, underlining the more general point that prevailing, accepted content and pedagogy may be the source of many misunderstandings. Implications are discussed and suggestions made for alternative treatments of these deceptively complex topics. (Contains 3 tables and 4 notes.)