How to survive a 500 foot fall

It's a modern-day miracle. An Ecuadoran native who fell 500 feet from the upper reaches of a New York City skyscraper--and survived. By the time Alcides Moreno hit the alley behind the black-glass luxury apartment building, he was traveling upward of 124mph. Only about half of the people who fall off a four-story building make it. So how is it possible that Moreno is alive?

The answer has a lot to do with physics, luck and a 16-foot plank.

Moreno and his brother Edgar, 30, both worked for City Wide Cleaners. They were getting ready to wash windows on Dec. 7, 2007, when the cables for the scaffolding snapped. Neither wore a safety harness. Edgar died instantly when he fell off the platform and a fence severed his body. But Moreno managed to grab ahold of the 16-foot scaffolding platform--which proved crucial to his fate.

Following the training provided by his company, Moreno held fast to the platform--which increased the air drag on his falling body. And when Moreno hit the ground, the 1,250-pound scaffolding absorbed some of the shock of the 5.5-second fall, which could have reached a terminal velocity of 124mph.

The terminal velocity refers to the point at which the acceleration of a falling object ceases. Gravity's downward pull gets counteracted by an upward push against an object. With no net force acting on the object, it cannot go any faster. Rumors that Moreno had "surfed" down the side of the building on the platform have no basis in science. But physicists believe the platform may well have saved his life.

"That plank produced a large surface area, much larger than his body, increasing the wind resistance and air drag," says James Kakalios, a physics professor at the University of Minnesota. "If there's no air resistance, only gravity pulls you down. As you go faster and faster, the air resistance becomes larger and acts as an upward force that oppose your [downward] motion."

Professor Kakalios cites a classic Spider-Man episode to explain what happens when a body in motion stops too soon. When the villain pushes the superhero's girlfriend, Gwen Stacy, off a bridge, Spider-Man caught her in his web. But her neck snapped and she died.

"That's one of the times that comic books got it right," said Kakalios, the author of "The Physics of Superheroes." "The force of the webbing was so great that her body could not handle it. Anytime something stops so abruptly, there's going to be great trauma on the body." In the comic, Gwen went from at least 95mph to zero in a split second--which means that Spider-Man was responsible for the death. He should have figured out a way to use his web to slow her descent before catching her. Reducing the deceleration--the rate at which an object comes to a stop--is critical to safety in high-speed vehicles like cars, spaceships, and even roller coasters.

If the platform Moreno clung to hit something on the way--like the side of the building--its momentum could have slowed. In effect, Moreno would have experienced several discrete falls rather than one single fall.

Moreno's landing also played a critical role in his survival... [Read More]

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