Boston slide cop video: The physics behind the viral descent.

Cops face plenty of perils in the line of duty—and now they can add an unusual one to the list. In a viral video that made the rounds last week, a uniformed Boston police officer spilled out of the City Hall Plaza playground slide face-down and rattled around like a soda vacating a vending machine. He suffered minor injuries, NBC10 Boston reported. But the incident provided some major entertainment.

Boston, MA - A Boston Police officer sustained a head injury after a mishap at a playground on Congress St downtown. Boston EMS treated the officer. pic.twitter.com/tVjsK2N252

While we only know how the officer exited the slide’s tunnel, not how he entered it, it does appear this mishap was entirely preventable: A sign notes that the slide, which opened last year following renovations to the plaza, is designed for children ages 2 to 12. The officer isn’t the only adult to disregard guidelines and take a tumble: Clips show that other grown-ups have met similar topsy-turvy fates in recent months on the same slide.

This slide has got to go #cityhall #Boston #governmentcenter #bostonteacher #teachersoftiktok #worldstar #blooper #teacher #sos #bostonparks #dumbwaystodieedit #concussion #massgeneralhospital #soundon #fyp

This content requires consent that you have not granted on Slate. To view this content pleasevisit www.tiktok.com or update your cookie preferences.

Learn more about this at our privacy page.

Now the playground’s memeification has encouraged crowds of adults to take a turn on the “Death Slide” and gamble on their fate. But why do some riders emerge unscathed from the tunnel, still in proper sliding position, while others end up upside down (and at risk of a concussion)? It turns out that there are a myriad of factors at play on the playground.

Grownups have taken over the playground. #Boston #Massachusetts #NewEngland #cityhallplazaboston #DowntownBoston #FaneuilHall #WestEndBoston #BostonCommon #MBTA #TDGarden #BostonPolice #BostonTikTok #BostonCheck #MassachusettsTikTok #MassachusettsCheck

This content requires consent that you have not granted on Slate. To view this content pleasevisit www.tiktok.com or update your cookie preferences.

Learn more about this at our privacy page.

It is not true, as many have surmised, that cop-sized adults travel down slides necessarily faster than children by dint of their weight. Children and adults should theoretically descend the slide at similar speeds. While more mass equals more gravitational force, objects with more mass speed up more slowly than lighter ones, Rhett Allain, an associate professor of physics at Southeastern Louisiana University, told HuffPost.

Instead, the high-speed accident may have resulted from the interaction between the materials composing the slide and the rider’s clothing—certain combinations create more friction than others. Generally, lower ratios of friction will allow people to move faster, said Michael Gilchrist, a professor of mechanical engineering at University College Dublin in Ireland.

So the officer’s uniform, which appeared to be composed of synthetic fabric, may have made his journey down the metal slide super slippery, Allain noted to HuffPost. Or he could have somehow stumbled onto the slide with his back to the entrance, Gilchrist suggested.

The slide design may well be to blame. “The problem is the twisting motion of the body induced by the curving path of the slide,” said Stephen Robinovitch, an expert in injury biomechanics at Simon Fraser University in Canada. “It’s like the banked corner of a luge.”

Thanks to the significant momentum induced by the downward journey and the sharp curves, some passengers seem to essentially swoop up to the side of the slide (sort of like one of those toilet bowl–esque water park rides).

In fact, Robinovitch predicts riders would fly off the edge if the final curved piece of the slide lacked any coverage. As it is, the configuration can potentially turn people’s bodies 180 degrees shortly before the sudden straight drop—the perfect recipe for injury.

“Normally, I think of the playground structures in the U.S. being more conservative than in Canada, due to the higher risk for lawsuits,” Robinovitch said. “In a way, this is a refreshing example of the opposite.” (Indeed, Canada has its fair share of slide-induced trauma: In 2017, the city of Edmonton removed a stainless steel model from multiple playgrounds after the United States–based manufacturer learned that the slides caused cuts and even finger amputations among U.S. children.)

It isn’t clear what exact injuries the cop experienced and what he was doing up there in the first place, but the Boston Police Department didn’t immediately respond to a request for comment.

For anyone looking to traverse slides safely, Gilchrist suggests “sliding feet-first in a face-upward position.” It could also help to stick to clothing with natural fibers when venturing onto metal chutes, Robinovitch said. Or just avoid structures designed for children.