In the First Law: Newton's first law of motion is that every object in motion will stay in motion, and an object at rest will stay at rest unless acted upon by an outside force. When someone skies there are two forces that are involved which is gravity and friction. The gravity holds the skier down on the slope and pulls them down the hills. Friction, which is between the skis and the snow; and the skier and air creates force that is directed opposite of the velocity. Skiing can be affected by this by just going straight down a slope. Since the Skier starts at rest they would stay at rest; if gravity didn't pull them down the slope. Once when the skier starts moving they must increase the friction between the skis and snow to either slow down or stop. Another way is that if a skier goes off a ramp and/or jump, then gravity would be pulling them down instead of remaining at a specific velocity. The momentum of the skier would be zero if at rest and the total momentum does not change if no net force acts on the object. (equation: p=mv)
In the Second Law: Newton's second law states that the acceleration of an object is equal to the total net force on an object (F=ma). In skiing, if a skier turns their skis to the side, the force of the friction of snow will be greater; oppose to going straight down the mountain. This reduces the net force and lessens the acceleration. But, if the skier pushes with poles, then the force off the pole will make the skier accelerate.
In the Third law: Newton's third law says that every action has an equal and opposite reaction. When equal and opposite forces act on the same object, they result in a net force of zero. In relation to skiing, when a skier turns the action would be the change of direction of force. The reaction is the snow blowing the opposite direction as your turning down the slope. When you push with poles, the force of the poles is going backwards, the snow pushes back and it makes the skier to accelerate forwards. Perhaps say that a skier runs into a tree off the side of the slope, the force of the skier is pushing on the tree and the tree pushes back on the skier with the same amount of force.
In this picture the skier is using the Third law of motion----the action: turning with the skis and showing the change of direction of force. The reaction: the snow pushing backwards. He is pushing with his poles so the force is going backwards and the snows pushes back creating more acceleration for the skier.
The laws through Olympic Skiing: In competitive skiing, the objective is to cross the finish line the fastest, while maintaining accurate and sharp turns and getting over and through the obstacles correctly. With physics, the skier speeds up more by reducing resistance to motion; from air resistance and snow resistance. The skier minimizes the air resistance (drag force) by reducing the front area. This is done by the skier bending down (which improves balance) that results in lower drag force. The drag force acts in the direction opposite of the skier's velocity, slowing them down. If you're going down the slope at a high speed and velocity while turning, bending down helps to regain and control your speed and balance that can prevent risk of injury.
This Olympic skier is bending down, and he is reducing the resistance to motion. The drag force is being minimized while going down the downhill slope at a fast speed with high velocity, bending down, helps him regain balance, speed, and control so he doesn't fall.
Resources: https://prezi.com/d1ub5jd1xber/how-do-newtons-laws-effect-skiing/. http://www.mcasco.com/Answers/qa_nlas.html. http://www.real-world-physics-problems.com/physics-of-skiing.html. https://www.youtube.com/watch?v=q0olDJhvK-A https://www.youtube.com/watchv=6cAkug0_2ok https://www.youtube.com/watch?v=SFoBXxEegjU&t=140s