Physics of Skiing "Cross Country"
In cross country skiing a skier can expect
to ski downhill, uphill, or across flat ground. Cross country
technique has been designed and perfected to fit all of the
travel expectations.
Downhill
A skier travels downhill (any kind not just
skate) by one of the most fundamental laws of physics; the
conservation of energy. An object, in our case a skier, wants
to be at the lowest possible energy. When a skier is on a hill
with and begins traveling down they will convert their
potential energy into kinetic energy by Newtons Second Law. At
the bottom of the hill, when the potential energy is at a
minimum, the kinetic energy will be at a maximum.
Skiers also can go into a "tuck". A tuck
makes a skier move their center of mass tighter in, and
increases their momentum.
Uphill and Flat
However, uphill and cross flat ground is a
bigger challenge than converting potential energy to kinetic
energy. To move a skate skier must use a combination of normal
force and friction. A skier pushed perpendicular to their ski
that pushes onto the snow at less than 90 degrees (the angle
the ski pushes onto the snow varies based off skier). The
interaction between the ski bases and snow uses friction to
push the skier forward.
For all uphill, downhill, and across flat
ground the kinetic energy of the ski across the snow is
converted to thermal energy. The thermal energy warms up the
snow to create a thin layer of liquid water for the ski to
move over. The next pages discuss how skiers use physics to
deal with different snow conditions.
image from: http://visual.merriam-webster.com/sports-games/winter-sports/cross-country-skiing/skating-step.php
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