Gravity is the force that holds the skier to the ground and is also what pulls the skier down the hill. While gravity is acting straight down on the skier, a normal force is exerted on the skier that opposes gravity. As the skier skis down the hill, he or she will encounter an acceleration. This acceleration is due to gravity caused by a change in the skiers velocity. The mass of a skier is different for every person and is easily calculated by multiplying a skiers weight in kilograms by the gravitational force exerted by the earth. These forces and more are explained throughout the rest of this web page.