Gliding for Gold: The Physics of Winter Sports

1. Solid Water—Sports and Science

1 SOLID WATER — SPORTS AND SCIENCE Welcome to the warm-up. In the next chapter you will be metaphorically hurled headfirst into the cold water of winter sports physics. By way of preparation, so that you may brace yourself, this chapter permits you to first dip a toe. Stated more mundanely (but also less alarmingly—I wouldn’t want you to think that reading this book is going to be like taking a cold bath), I will spend a chapter describing these winter sports. More: you will need to know something about the ice and snow surfaces they are played on, and be brought up to speed about the frictional forces that act upon athletes and their equipment. So, first an overview of winter sports (those which are included in the Winter Olympic Games), second a description of the interesting and unusual physical properties of ice and snow, and third an introduction to the physics of sliding friction and of aerodynamic drag. L E T T H E G A M E S B E G I N The Winter Olympic Games are a modern invention that began in Chamonix , France, in 1924. The last such games were held in Vancouver, Canada, in 2010, and the next will be in Sochi, Russia, in 2014. As we will see, not all of the sports began in Chamonix. Some—particularly the women’s events—are much more recent. Here is the list of Winter Olympic sports that are played on ice: ≤ bobsled ≤ luge ≤ skeleton ≤ figure skating (including ice dancing) ≤ long-track speed skating SOLID WATER — SPORTS AND SCIENCE 5 ≤ short-track speed skating ≤ ice hockey ≤ curling And on the flu≈er form of solid water, these sports are played: ≤ alpine skiing ≤ snowboarding ≤ cross-country skiing ≤ ski jumping ≤ biathlon ≤ nordic combined The 2010 Games were divided into 86 events (up from the original number of 16). Over half of them come from four sports: speed skating, crosscountry skiing, alpine skiing, and biathlon. Given that you are reading this book, it seems likely that you are familiar with one or two of these sports—perhaps you sweep, or poptart, or hotdog, or axel. Even so, the majority of winter sports may still be something of a mystery to you, and so, to clarify fuzzy notions, I will here provide a brief description of each. Bobsled. Two-man, four-man, or two-woman bobsleds hurtle down artificial tracks that are typically 1,250 meters long (with about 15 bends). Bobsleds are steered. Competitors begin from a standing start and push their sled as much as 50 meters (hereafter abbreviated ‘‘m’’) before boarding . This sport has been part of the Winter Olympics since its inception and has been dominated by American, German, and Swiss athletes. Luge. One or two men (or one woman) jump onto a sled feet first, on their backs, and steer down the bobsled track. As with bobsled and skeleton , multiple runs are timed to decide the winner. Germans and Italians have been particularly successful at luge events, which have been part of the Winter Olympics since 1964. Skeleton. One athlete dives onto a small sled, which uses the same track as for bobsled events. The skeleton competitor lies prone, facing forward, and steers by body movement only. Skeleton sledding has been an Olympic event (for both men and women) only since 2002 and has been dominated by U.S. athletes. Figure skating. Single skaters and pairs (including ‘‘mixed doubles’’ for 6 GLIDING FOR GOLD ice dancing events) perform maneuvers—jumps, rotations, lifts, and combinations —of varying di≈culty over a set time and are awarded points for their performance of each maneuver. An Olympic sport since 1924, figure skating has been dominated by Soviet and Russian skaters. Long-track speed skating. Long-track skating competitions are timed events over set distances, around an oval track. Usually competitors start in pairs (at opposite ends of the oval, for team pursuit events). Distances vary from 500 to 10,000 m, although there is also a 40-kilometer (km) marathon (with a mass start). Very popular with the Dutch, speed skating has been an Olympic event for men since 1924; women’s events did not appear until 1960. Short-track speed skating. Short-track skating events are races (final position is all that matters) each with a mass start of four to six skaters, on a short oval track of circumference...