This setup in the lab helped researchers track movement using swings and markers attached to swings
Chiaki Hirata et al./APS 2023
Whether the fore-and-aft arc of the playground swing grows over time depends on how the person sitting on the swing moves against the swing. Many children seem to intuitively understand this phenomenon. Now physicists determine exactly when to lean back and swing higher while on a swing.
“Kids don’t know the laws of physics, but they nevertheless somehow embody them and swing very well,” says Chiaki Hirata of Jumonji University in Japan. He and his colleagues used the laws of physics and swinger observations to determine some rules for making the swing high.
Researchers have derived an equation of swing motion that explains how the person on the swing can lean back and forward at any point in the swing’s arc. We then solved these equations for swings of different sizes and sequences of different upper-body movements to identify the combination that gave the highest swing elevation from one forward-backward oscillation to the next.
Researchers have found that the best time to lean over depends on how high your swing is already. If the arc is small, like at the beginning of the swing, the person needs to move the upper body backward as the swing is at the bottom of the arc and moving forward. After doing this a few times, the swing should start to get higher and the person should start leaning back more quickly when the swing is in the furthest part of the backswing.
Hirata and his colleagues wanted to see how the model matched a real playground swing, so they built a swing in the lab and had 10 college students try it out. They all said they had played on the swing before, but they had never been explicitly taught how to move for a higher swing.
The researchers attached a total of 10 special markers to both the swing and the participants and recorded the swing with a camera for approximately one minute at a time. is consistent with the rules derived from the mathematical model.
Hirata says the agreement leads to more questions. “How do swingers manage to move their bodies so well? It’s hard to believe they’re moving on purpose because they need to adjust their bodies in 10-millisecond increments,” he said. increase.
The researchers’ current hypothesis is that swingers are unconsciously responding to forces like centrifugal force that push them back. They want to test this idea and have their students use the playground swings in a virtual reality where these powers may not exist.
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