In children鈥檚 playgrounds, I am always confounded by how the slipperiness of the same slide can vary hugely throughout the day, and on different days. What factors influence this?
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Rob Wheway Children鈥檚 Play Advisory Service, Coventry, UK
Speed differences of children going down playground slides is primarily due to the clothes they are wearing. Synthetics (nylon/polyester) give a faster speed than cotton/denim. The speeds can range between too fast for safety (very occasionally) and too slow to be fun.
The seasons, weather and time of day will determine the clothes worn rather than having a direct influence. The size and weight of a child doesn鈥檛 appear to have a significant effect.
Some slides become too slow within a year and need to be polished to bring back their utility. This is probably due to a build up of rubber scuffing from soles of shoes, but I can鈥檛 be certain.
When consulted on playgrounds, children and parents request bigger and faster slides, which demonstrates that slides are still popular and that people today aren鈥檛 risk averse, as is commonly supposed.
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Stuart Reiss, via Facebook
There is a formula for this. MICCF 脳 FR (Melted Ice Cream Cohesion Factor multiplied by Fabric Resistance).
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Geoff Convery Lincolnshire, UK
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Most, if not all, of the difference in slipperiness of children鈥檚 slides will be due to the amount of water on their surfaces.
Ambient humidity varies greatly, both day to day and over the course of the same day, and this will affect the amount of water on the slide. Early in the morning, humidity tends to be higher and the temperature lower, so any given slide will probably be quite wet. If it is warm and sunny, the water will evaporate.
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Chris Szymonski Waupaca, Wisconsin, US
The tribology, or 鈥渟lipperiness鈥�, of playground slides is a function of temperature, relative humidity of the air, the material of the slide and the fabric of children鈥檚 clothes.
A very thin layer of water covers surfaces. This can act as a lubricant if the clothing worn by the slider is synthetic and water-repellent, but not if it is hydrophilic and water loving, such as cotton.
There may be more water on the slide on a cool, humid morning than on a sunny afternoon. In addition, older slides made of zinc-passivated steel are more hydrophilic than newer slides made of plastic.
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@throwatwitfit, via Twitter
The answer depends on how much sunscreen little Freddie鈥檚 mum slathered him with today.
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Katherine Rose, via Facebook
The weather and clothes have a big impact. One surprisingly fast slide run occurred on a damp day when my daughter was wearing waterproofs. It was so fast that she shot off the end of the slide. We think that the water built up in a layer between the slide surface and the waterproofs, making the combination extra slippery.
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Mike Follows Sutton Coldfield, West Midlands, UK
The presence of water can change the coefficient of friction between two surfaces. I slipped over on a steep grassy slope during a downpour while wearing a waterproof jacket and trousers. Much to the amusement of friends, I ended up sliding a considerable distance.
The waterproof material had become separated from the grass underneath by a thin layer of water. This is the same mechanism that causes a vehicle to aquaplane.
It might have been a different story if I hadn鈥檛 bothered putting on my waterproof overtrousers. The water would have been absorbed by the rougher hydrophilic fabric of my walking trousers and this might have ensured contact (and friction) between the two surfaces.
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Lesley Clayton Truro, Cornwall, UK
If you lived in Trowbridge, a town in the UK, and you were a child in the late 1940s, the answer to this question would be that it was slipperiest around late morning to lunchtime. This is because the margarine that my mother and her sisters applied to the top of the slide first thing in the morning would, by then, be coating the whole length of the slide.
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