How Do Skiers Go So Fast?

By minimizing air resistance. Friction between ski and snow is very small, so the main drag on speed is the wall of air in front of the skier. Skiers can cut air resistance by decreasing their frontal area: maintaining a tight tuck, having boot buckles flush with the boot and using poles that curve around the body so the baskets hide behind the back. Other factors being equal, a heavier skier is faster than a lighter one because his air resistance is lower. So a skier can go faster by increasing mass--becoming as heavy as possible for his frame. Only at about 200 pounds does the advantage of extra weight get wiped out by the increased friction with the snow.

Are longer skis faster? The length is a compromise between one that will exert the least pressure on the snow and one that can still be turned. A longer ski exerts fewer pounds per square inch of pressure, and so is less likely to wind up plowing rather than gliding. But a longer ski is also more difficult to whip around for a downhill turn or a slalom gate. Downhill racers are choosing 220- to 225-centimeter skis (about 87 inches); slalom competitors, 204 to 207s (about 81 inches).