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Swedish tribologists debunk old theories and offer a new one that fits all the facts!
CURLING IS AN OLYMPIC SPORT PLAYED ON ICE that is enormously popular in northern countries such as Canada, Scotland and Sweden. It involves two teams that slide a series of 16 stones along a 28-meter stretch of ice, aiming to get them as close to the target as possible. Once the stone is released at one end of the ice sheet, the trajectory is governed purely by sliding friction.
The subtlety of the game is that by rotating the stone upon release (producing 1-3 rotations over the entire 28 meters), the stones can adopt a curled trajectory, thereby avoiding "guarding" stones that would otherwise prevent the moving stone from accessing the target, as shown in the figure.
Harald Nyberg of the Angstrom Tribomaterials Group, University of Uppsala, Sweden, along with colleagues Sture Hogmark, Staffan Jacobson and Sara Alfredsson, have recently published two landmark papers on this inherently tribological sport. One [1] of these discounts old theories, while the other [2] proposes a novel theory that appears to account for all observations to date. It is important to know that the bottom of the stone is hollowed out such that the contact with...