Read this introduction to a magazine article. your hands are up, your eyes are squeezed tight, your mouth is poised to unleash a scream . . you are on a roller coaster. but are you recalling science-class lessons about gravity and inertia? are you contemplating the gears and mechanisms providing this thrill? it is unlikely that academics are on your mind, but lessons are lurking behind every ride. what will most likely be included in the magazine article that follows this introduction? a) a description of the history of roller coasters b) criticisms about roller-coaster safety c) testimony from roller-coaster enthusiasts d) an explanation of the physics of roller coasters