The picture above illustrates that the force
of gravity is acting in the downward direction on the skier, with a force
of the skier's mass times the acceleration of gravity. The acceleration
of gravity is about 9.81 m/s2. However, from the illustration
above it is clear that the block-skier is skiing uphill at the angle theta.
In order to calculate the force acting on the skier in the directions parallel
and perpendicular to the hill, the mg must be separated into two parts.
By separating mg into parts, it becomes clear that the force of gravity
pulling a skier down the hill is m*g*sin(theta).
Skiers must consider the force of gravity when choosing equipment. This
is because a person's weight and therefore downward pull affects equipment
setup. A heavier person might need stiffer skis, whereas a light person
may prefer more flexible ones.
Gravity is extremely important in cross country skiing. Without it,
going uphill would not be the same. Some people might think skiing
uphill would be easier without a force pulling you down the hill. However,
gravity also is responsible for keeping you "stuck" to the hill to begin
with. Without gravity a skier would be free to float around, and that
would probably be the end of skiing right there.