An international coterie of physicists have determined the ultimate technique for using a playground swing, and I’m happy to report you have probably been doing things correctly your entire life.
In their paper “Initial phase and frequency modulations of pumping a playground swing” in the journal Physical Review E, Chiaki Hirata and four other physicists from Japan and Australia compared different mathematical models and real-world swinging data collected from volunteers to determine the most efficient way to swing, which is as follows:
At the beginning stage of the swing session, when you have less momentum, lean all the way back just as the swing moves forward past the equilibrium point (that is, when the chains are vertical.)Once you really get going, the optimum point to begin leaning back is earlier—at the highest point in the backward swing, right before you start going forward.To be fair to Hirata, et al, the point of their research was not actually to determine optimal swinging efficiency at the playground, but to provide a more realistic model for the field of swing-based physics research (which is, I assure you, a real thing). The paper compared their own model of swinging with both the “fixed frequency” swinging model and the “square-wave” model, and found a combination of both yields results closer to that of real-world swinging.
How do you actually know how to swing?
If you read the above and thought, “No shit. I’ve been swinging like that since the second grade,” it might be valuable to consider how you learned to swing in the first place. Using a playground swing (or a “dynamic, coupled oscillator,” according to Science) is difficult to describe precisely, and how we are able to work swings so effortlessly is fairly mysterious.
To paraphrase the paper: Choosing the right time to shift your weight during a single swing cycle is relatively simple, but each time the swing goes back and forth gaining momentum, the window gets shorter. Their example points to a 7 millisecond shift per cycle—an extremely short amount of time to react—but as children, we somehow manage to master swinging quickly, without thinking about it.
The scientists’ proposed explanation is that our bodies are attuned to the centrifugal forces at play, and when swinging, we’re subtly shifting our movement in response to the forces acting on us without really being conscious of it. Imagine trying to describe exactly how to swing to someone who isn’t on or has never seen a playground: ”It’s like, you lean back just when you feel like it’s time to lean back—”
The paper suggests further research using a virtual reality swing to remove the variable of physical feedback, positing that we’d have a difficult time getting a swing to high velocity without momentum and other forces guiding our movements. I, for one, eagerly await the breeching of these new frontiers in experimental swing-based physics.
