We report the first derivation of the coefficient of friction between bobsleigh runners and ice from experimental measurements performed in a controlled environment. In a series of experiments on both horizontal ice and a track sloped at 6.80°, a radar gun was used to sample the speed of a moving sled in the range of (1-10) m/s at a sample rate of 31.25 Hz. The acceleration of the sled, and thus the coefficient of friction, was extracted from these data, with a value of (4.2 ± 0.9) 9 10 -3 for the coefficient of friction associated with a set of two-man bobsleigh runners. There was no detectable variation in the coefficient of friction with velocity at this range of speeds and experimental accuracy. This result improves our knowledge of this coefficient over currently accepted values determined from indirect measurements, and indicates that the coefficient is lower than the currently accepted range.
Top short track speed skaters and their coaches have suspected that starting positions influence finishing positions, especially in the 500 m racing distance. The objective of this study was to examine systematically the influence of starting position on finishing position in 500 m short track speed skating. The data analysed included results from World Cup 500 m races ranging from the 1999-2000 season through to the end of the 2003-2004 season. All 500 m men's and women's races with four skaters starting and finishing (preliminaries, heats, quarter-finals, semi-finals and finals) were included in the data set. The association between starting position and finishing position was examined using Kendall's tau. Results show that for both sexes, there is a significant positive correlation between starting position and finishing position (P<0.001). This effect is generally more pronounced in semi-finals and finals than it is in preliminaries, heats and quarter-finals. Strategies to counter this inequity are proposed, drawing upon similar experiences in other sports.
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