Two swings

What you can do here
  1. Swing only one of the swings, the other one should remain static. When the amplitude of the first swing is noticeable, let them move freely. What happens?
  2. Try swinging in such a way that the swings move in the same direction at the same time – this is symmetric oscillation.
  3. Try swinging in such a manner that the swings move in the opposite directions at the same time – this is antisymmetric oscillation.

How it works
The two swings are connected with a rope and make a set of coupled pendulums. By sitting on one swing you become part of that model. When one person swings and they both let their swings move freely, you see the phenomenon of oscillation conveyance: the immobile swing starts moving, reaching its highest amplitude. At the same time, the amplitude of the other swing decreases. After some time the cycle repeats. The process does not loop infinitely because of air resistance and friction acting on the swings.


Interesting facts
Transmission of vibration is very often an undesirable effect. Oscillations of small frequencies are particularly dangerous as they are transferred to people working with machines and devices in material processing (drilling, crashing, grinding). The problem also pertains to communication and transport –in cars, buses, planes and trains, you experience transmission of vibrations as well.