The interplay between potential and kinetic energy is at the heart of pendulum and roller coaster motion. Even if some energy is always converted to heat during a swing or throughout a roller coaster ride, the losses are sufficiently small that changes in potential energy  can be used to estimate changes in speed, through the corresponding changes in kinetic energy. The examples in the chapter include a roller coaster loop as well as the influence of the position in the train.

The initial energy for a roller coaster train is traditionally provided in the in the form of increased gravitational potential energy, in the lifthill, where a chain (or other device) pulls the train to the highest point ot the track. Many modern roller coasters instead give the train initial kinetic energy in the form of a launch. The chapter offers a deeper dive into the energy conversions during a hydraulic launch, as well as the heating and cooling of magnetic brakes at the end of the ride.

Keywords: work, energy, friction, free fall, energy transformations, acceleration, loop, magnetic brake, heating

• Acceleration in 1, 2, and 3 dimensions in launched roller coasters, Pendrill, A-M, (2008) Physics Education 43, 483-491
• Stopping a roller coaster train, Pendrill A-M, Karlsteen, M and Rödjegård, H (2012),  Physics Education 47 (6), 728 (including a video abstract and an IR movie)
• Student investigations of forces in a roller coaster loop, Pendrill A-M (2013), European Journal of Physics, 34 1379 (Manuscript)  (also "Fram mitten eller bak - var ska man sitta?" LMNT-nytt, nr 2 2013.)
• Students making sense of motion in a vertical roller coaster loop, Pendrill A-M, Eriksson M, Eriksson U, Svensson K and Ouattara L 2019 Physics Education 54 065017
• Pendulum rides, rotation and the Coriolis effect, Pendrill A-M and Modig C 2018 Physics Education 53 4 045017 (video abstract + Swedish video abstract)
• Roller coaster loop shapes revisited, Pendrill A-M  Physics Education, 51 (3) 030106 2016 (Free article, selected for the volume Physics Education 50 years)
• Serious physics on a playground swing, Pendrill A-M 2023, The Physics Teacher 61, 355
• Comment on Pendulum: the partial and global approach, Pendrill A-M 2023, Physics Education 58 018001