The purpose of this assessment probe is to elicit students’ ideas about circular motion. It is designed to determine whether students recognize that an object will move in a straight line unless acted upon by an outside force. Elementary students may have played with curved marble towers, but at this level their experiences are observational. At the middle level, force and motion relationships are developed more fully so students learn about Newton’s first law of motion and a variety of phenomena that can be explained by it. High school students build on their previous experience with Newton’s first law, adding mathematical relationships to their understandings. Teacher notes, standards, assessment, and references are provided. This book selection also includes the Table of Contents, Dedication, Preface, Introduction, and Index.