Physical Forces Cross-country skiing uses a variety of physical forces. Mostly is skiing dependent on friction, gravity, drag, and pushing force created by a skier. Friction - a force that all skiers need, but often don't like. Friction is created between the contact of snow and ski bases. Friction can either help a skier or slow him down. In order to glide faster, the less friction between the snow and skis, the better. Once the skiers start using their legs to push from snow and increase speed through that the friction is necessary. A graph of  friction in skiing from https://www.wikiwand.com/en/Ski_wax Before ski can start gliding it needs to exceed the static friction . The colder the temperatures the larger the friction. Gravity - a force that keeps the skiers on the snow, helps them glide fast on the downhills (momentum is also needed), and makes the uphills painful. The larger the skiers mass the more the gravity affects their velocity.  Drag - also known as air resistance, is a force that matters the most on high speeds, when the air tries to slow the skiers down. Skiers use a special technique called tucking on the downhills to reduce the air resistance. The pushing force - is the force created by the skier by pushing with their skis and poles. This is the force that makes the difference between fast and slow skier, as the larger skis force the larger the acceleration and velocity.