Circular motion in a vertical plane involves a large variation of possible motions, with the centripetal acceleration pointing in any direction between up, horizontal and down and the force from the ride combining with gravity in a way that changes continuously. The different ride examples highlight that the body moving may rotate around different axes - or not at all. They aim to increase the awareness of the orientation of the body and of forces and rotation around different axes. This chapter also prepares students for rigid-body dynamics in three dimensions, which is known to be a challenging aspect of engineering mechanics. Rotation axes are less abstract when they involve our own extended bodies. A few cases of uniform circular motion, from slow moving Ferris wheels, to classical family or thrill rides are discussed, before continuing with non-uniform circular motion, including Flying carpets. Finally, a few examples of combined circular motions are introduced. Pendulum motion and roller coasters loops, where the tangential forces from the ride are negligible, will be discussed in chapters 7 and 8.

Keywords: circular motion, carousels, acceleration, smartphones, graphs, biomechanical coordinate system, pressure sensor, free-body diagrams