One person should set their swing in motion while the other should keep theirs motionless. When the oscillation amplitude is large enough, both participants let their swings move freely. How will the swings behave? Try to swing in such a way that both swings move in the same direction at the same time – this is a symmetric oscillation. Then, try to swing in such a way that both swings move in the opposite directions at the same time – this is an asymmetric oscillation.
Two swings joined with a rope form a model of coupled pendulums. We become part of this model by sitting in a swing; when one person swings their seat and then they both let their swings move freely, we can see the vibration transference phenomenon: the swing that has been still is now beginning to swing with an increasingly large amplitude. Simultaneously, the oscillation amplitude of the first swing is decreasing. The cycle is repeated after a while. It finally ends due to the drag and friction in the system.