Hoffman begins a ride by dangling off the top of one side of a half-pipe. There, he has gravitational potential energy (stored energy due to height).
Because average half-pipe ramps are only 3 m (11 ft) high, daredevil HoffMan built a taller model off the side of a building.
But as iris bike rolls across the half-pipe, friction (resistance to movement when two surfaces rub together) between his tires and the ramp acts like a brake.
As he accelerates (changes velocity over time) up the curve of a half-pipe, the acceleration creates a force, called a G-force, on his body.
"The faster he's going through the half-pipe, the more acceleration there is, and the bigger force he feels," explains Pollock.
Hitting a half-pipe much faster could spell trouble.
Unlike the giant slalom, the level, symmetrical course also used in official snowboarding events, the half-pipe course resembles a cylinder cut lengthwise.
In snowboarding's infancy during the late 1960s and early 1970s, ski resorts used snow cats, the 250-horsepower tracked excavators made by such companies as LMC in Logan, Utah, and Bombardier in Granby, Quebec, to back-cut or traverse-cut half-pipe walls.
In 1990, Maxey Inc., a trailer- and snow-grooming-equipment company in Fort Collins, Colo., decided to commission Doug Waugh to design a machine that could finish a half-pipe course roughed out by a snow cat.
Waugh completed his assignment, but Maxey was unsure that half-pipe courses were viable.
Honored to create and maintain the first Olympic half-pipe course, Waugh will make the course using the latest-generation Pipe Dragon.