A formula for making playground swings go higher has been unveiled by scientists. The contraptions help kids develop their agility, speed, strength, balance and coordination.
Many understand instinctively exactly when they should lean back to achieve the optimum arc. Lead author Dr Chiaki Hirata, of Jumonji University in Japan, said: "Children don't know the laws of physics - but they somehow embody them."
The Japanese team worked out equations for a swing's motion that account for a person leaning backwards or forwards at any point. They then solved them for various sizes of swings and sequences of upper body motions - determining which combination made a swing gain the most altitude from one back-and-forth oscillation to the next.
When the arc is small - as it is when you first start - the person should move their upper body backwards when the swing is at the bottom and moving forward.
After gaining height they should start leaning back earlier - when the swing is at the furthest part of the backswing, reports New Scientist. To test whether people intuitively knew to do this, the researchers built a swing in a lab and recruited 10 college students to try it.
All said they had played on swings before, but had never explicitly been taught how to move to get the swing to go higher. When they studied footage of their experiment, the team found participants naturally matched the rules derived from their mathematical model.
The findings lead to even more questions. Dr Hirata said: "How do the swingers shift their body so well? It's hard to believe they are moving intentionally because they must adjust their body as quickly as in 10 milliseconds."
The researchers believe swingers are subconsciously reacting to some centrifugal-like force that is pushing them back. They want to test this idea on swings in virtual reality where those forces shouldn't exist.
The modern-day swing found in playgrounds is the product of an English engineer, Charles Wicksteed, and was developed in the early 1900s. Since then, swings have gone through many different iterations, including tire and multi-user swings.
