NYTimes.com:
Freestyle aerialists, skiers that hurtle off a curved ramp at
30 miles per hour, soaring six stories in the air while doing
three back flips and up to five body twists, are not actually
throwing caution to the winds. It is not fate that plops them
down at the end of their jumps, more or less upright and safe,
in a cloud of powdery snow. It is physics, and plenty of
preparation."The forces are pretty simple," said
Adam Johnston,
a physics professor at Weber State University in Ogden,
Utah."There's the force of the ramp on his skis, and the force
of gravity on him," Johnston said, after
Ryan St. Onge, the
reigning world champion in men's aerials, zipped down a steep
inrun, leaned back as he entered the curved ramp until he was
nearly horizontal, and flew off at a 70-degree angle.But it is
enough to create torque that sends St. Onge somersaulting
backward as he takes to the air, arcing toward a landing on a
steep downslope that the skiers and coaches have chopped and
fluffed for safety."Once he's in the air, the only force on him
is gravity," Johnston said. "You could trace his center of mass
as a perfect parabola through the whole thing. From the physics
point of view, that's one of the beautiful things."
