Sometimes Olympic dreams and physics are on an unenviable collision course.
Athletes have literally crashed out of competition, ending their quests for a medal by smashing into siding, toppling over amid a crowded cross-country skiing field or simply pitching face-first into the snow. Their hopes live and die on the edge of their skate, snowboard or ski.
For a public accustomed to watching Olympians flawlessly execute superhuman feats, a tussle with gravity is a reminder that even athletes in the most rarefied of circles are all too human.
