an Almost perpetual motion machine.
Perpetual motion is motion that continues indefinitely without any external source of energy. meaning a system in perpetual motion will never stop going, so efficiency is 100% or more - meaning either no energy is ever lost in the system or a surplus “free” energy is generated.
this is theoretically impossible as it violates the first law of thermodynamics (that is the law of conservation of energy that states that energy can neither be created nor destroyed). however, the above set up is one of the closest ever gotten to perpetual energy with an efficiency of 80-99%, an internal combustion engine in a car has around 30% for comparison.
at up to 99%, the rolling ball can continue rolling for years on its own, but will at some point stop. only at 100% efficiency is it perpetual which is not theoretically possible.