Racing Rings consists of three rods one each of copper, aluminum and PVC, Ring magnet is dropped down the PVC rod, it falls unobstructed, Two metal rods create an induced magnetic field to that adds resistance to the rings travel, metals are different, they fall at different rates
Boyle's law Horizontal apparatus, A horizontally mounted acrylic tube having a graduated scale (0-300cm3) along one side. A gas tap closes the tube. Pressure gauge is present next to gas tap.