Skateboarders rock physics

Experienced riders show gut knowledge of slope speeds

SEATTLE — Skateboard freaks know some righteous physics, dude. That’s because their hair-raising rides provide body-based insights into slope speeds that often elude those without a need for thrills and spills.

A ball travels faster down a relatively long incline that angles steeply downward in two sections separated by a flat stretch compared with a shorter incline that angles downward modestly but without changing slope. People generally don’t realize this, but experienced skateboarders often do, said psychologist Michael McBeath of Arizona State University in Tempe. Skateboarders call on motor memory to determine intuitively that a sharp early descent creates a speed advantage, he reported November 5 at the annual meeting of the Psychonomic Society.

“This is a hard problem, even for physics professors that we quizzed, but skateboarding experience improves estimates of slope speeds,” McBeath said.

People use prior bodily experiences to solve theoretical problems such as how fast objects move down various slopes, he proposed. Physics teachers might consider exploiting whatever body-based knowledge students possess, such as telling youngsters to imagine themselves as the ball rolling down different inclines, McBeath suggested.

Among 122 college students shown drawings of a longer, steeply angled incline and a shorter, straight incline, only 27 percent realized that a ball would travel faster down the longer path, McBeath and his colleagues found. Intriguingly, a few students known to be avid skateboarders solved the problem correctly.

McBeath’s team then recruited 41 volunteers — mostly males, who had skateboarded for anywhere from about six months to 15 years — at a nearby skateboarding park. One area of the park contained adjacent slopes, one flat and one with a pair of bumps, much as in the classroom problem. Participants told to skateboard as fast as possible down one of these slopes picked the bumpy path on 75 percent of runs. The bumpy slope consistently produced faster rides.

When given the classroom problem, 61 percent of skateboarders got it right. Those who answered correctly tended to be the most experienced skateboarders.

Skateboarders may have picked the faster slope at the park because they knew from past rides which incline was speedier, suggested Stanford University psychologist Barbara Tversky. Challenging skateboarders with unfamiliar slopes might reveal ways in which their intuitions fall short, she said.

Bruce Bower has written about the behavioral sciences for Science News since 1984. He writes about psychology, anthropology, archaeology and mental health issues.

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