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December 2, 2005

Strange But True!

Q. From an Elmira, Ontario reader: "My visiting aunt became concerned that the kids on the swingset were going too high and might swing all the way around ... like she did as a kid. We don't believe her story. She insists she did a complete 360 around the top bar. Would it be possible for a kid to gain the momentum to do this?"

A. The centripetal force would need to be at least equal to gravity to keep some tension in the chains at the top, which for chains 2 meters long would require the child to go at 4.4 meters per second at the top — not too fast, says Yale University mechanical engineering professor David LaVan. However, this would mean higher velocity at the bottom of the arc, which works out to be about 10 meters per second (22 mph) — or about the speed of an Olympic sprinter. So: conceivable, albeit unlikely.


 
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