Downhill skiers are racing down Vancouver’s Whistler Mountain at speeds up to 90 miles per hour. Alpine skiing is a downhill thrill ride where skiers try to get down the mountain as fast as they can. In the process, they use Newton’s Second Law of Motion: force on an object produces acceleration.
Force is created by the skier kicking out of the gate and pushing on the snow while the object or the skier produces an initial surge of acceleration down the slope. Then one of the fundamental forces of physics – gravity takes over.
Gravity accelerates the skier down the hill at ever increasing speed, but another force is also at work to slow the skier. Friction. It’s created when the bottom of the ski rubs against the surface of the snow. The skiers trade acceleration for control, using the friction between their skis and the snow.
How the skier holds their skis on the snow impacts their speed. The frictional forces of the snow can be reduced by perfectly edging or floating across the snow. Edging the skis causes one side to dig in, slowing the skier down but allowing them to make alternating right and left turns. In straightaways, keeping the ski flat on the snow causes the ski to sink less and maintains higher speed.
Another source of friction for skiers is wind or air resistance, which also slows their decent. Skiers try to minimize this by keeping their bodies small and tucked in.
Eliminating wind resistance also involves finding the shortest path down the hill and staying close to the surface on jumps. If the skier goes higher in a jump, they spend more time in the air, creating more wind resistance. They do not want to lose speed in the air.
By assessing the curve of the slope, the skier can find the shortest route down the hill. Finding the perfect line down the hill is the art of going fast and crossing the finish line the fastest.