# Metronome synchronisation applied to swings

The movement of several metronomes can be synchronised when a movable floor is utilised which couples the movement of the different metronomes.

Is it possible to apply this sort of synchronisation to several swings occupied by people (the ones you have on children playgrounds)?

I visualise this as several swings connected to a rigid platform that is free to move parallel to the ground. I assume that the length of each swing line ($L$) is the same and that the length of the swing line is the only factor that influences the swing period ($T$) according to:

$$T = 2 \cdot \pi \cdot \sqrt\frac{L}{g}$$

I understand that the metronome is driven by a wound spring and that this part is not present in a swing. People can move their c.o.g. back and forth during the swing, emulating the effect of the spring.

Can the principles present in the metronome sync be carried over to swing sync such that swings start swaying together after a certain amount of time?
Are my assumptions correct? Which additional assumptions do I need to make this work?

• have a look youtube.com/watch?v=4bWgczaOL-c Mar 27 '13 at 4:51
• finally this answers it ? youtube.com/watch?v=iklVYPfJSQY Mar 27 '13 at 5:05
• @annav Thanks for the links, but these motions are not really coupled in the same way as the metronomes are. Is that a big difference? Mar 27 '13 at 7:10
• the last link is close to the metronome, as the string suspension transmits energy from one to the other . Mar 27 '13 at 9:07

The experiment shown in the video would probably work with ordinary pendulums as well as with metronomes, if they only sustain their movement long enough.

There might be some practical problems with getting this to work with human swings. Swings don't usually line up along their plane of movement, so the platform might start to rotate when the swings are out of sync, if it has the freedom to do so. Also, the people in the swings should probably not move back and forth. If they did, the effect of this quite irregular movement would probably outweigh the syncing effect.