The Physics Behind Skiing

The Physics Behind Skiing 

I grew up in the Pocono Mountains, an area centered around winter sports. Because of my prime location in the Appalachians, I was exposed to Alpine skiing and snowboarding at an early age. My sister and I would often attend the weekly ski races at the local ski slope. Eventually, I became a children’s ski instructor at the age of 15 and occasionally taught snowboarder lessons. These experiences led me to become interested in the physics that I was unknowingly using and teaching. 

First, alpine skiing is when an individual skis down a hill (this is not to be confused with cross country skiing which involves flat and inclined terrain). Alpine skiing utilizes the theory of conservation of energy. Essentially, a skier gains speed by converting gravitational energy to kinetic energy. This gif explains the physics behind skiing very well. 

Source:https://www.physicsclassroom.com/mmedia/energy/se.cfm

I decided to calculate the angle of the slope of the hill that the skier is skiing down in this gif. For now, let’s assume that on the hill there is no friction, or air resistance. We can also assume these values.

H= 52 m  

Vo= 0 m/s 

Vf = 31.9 m/s 

t= 10s

Coordinate System:

 

Calculations: 

vf = vo + at

31.9 m/s = 0 m/s + a (10s)

a=  3.19 m/s2

vf 2 = vo 2 + 2a(xf − xo )

(31.9 m/s)2= (0 m/s) 2 + 2(3.19 m/s2 )(0 − xo )

Distance traveled = 159.5 m 

sinθ = opposite/ hypotenuse

sinθ = 52 m/ 159.5 m

θ= 20°

There are a few nonconservative forces involved in skiing such as: air resistance, forces that the skier enacts on the skis, and friction from the snow.

Source: https://prezi.com/u0okyv24acz2/physics-of-skiing/

Minimizing or maximizing forces can be beneficial to skiers in different situations. For example, in a ski race, a skier would want to maximize forces working in the downhill direction, and minimize forces acting in the uphill direction. Conversely, if a skier is trying to slow down or stop, a skier would want to minimize the amount of forces acting in a downhill direction and maximize those acting in an uphill direction. 

This made me think back to my time as a children’s ski instructor. When teaching beginner children skiers to stop, turn, or speed up I would use two terms: “pizza” and “french fry”....

Source:https://sites.psu.edu/cptpassionblog/2015/09/18/pizza-and-french-fries-2/

“Pizza” is the term I used when I was concerned with speed control and stopping. When I told a student to make a pizza with their skis, they would create a wedge with their skis, bringing the front tips of their skis closer and separating the back end of their skis. 

Source: https://unofficialnetworks.com/2012/03/05/pizza-amazing-ski-epic-pov/

Creating a pizza maximizes the frictional force acting against the skis (which acts in an uphill direction), allowing the skier to slow down. 

“French fry” is the term I used when I wanted my students to begin to get comfortable with skiing faster. When I told the students to make french fries they would straighten out there skis so that they were parallel to each other.

 

Source: https://www.theadventurejunkies.com/how-to-turn-on-skis/

Making french fries minimizes the frictional force acting on the skis and makes the skier go faster.