The Science Behind the Slopes

It’s that time of year! Over the next few weeks, many schools will be taking a week off for a mid-winter break.  Many families will be headed to slopes to go skiing.  (The small book “Skiing” by Henry Beard and Roy McKie defines skiing as: “the art of catching a cold and going broke while rapidly heading nowhere at great personal risk.”)  Skiing is a past-time for many of us in New England, and we stay glued to the weather report in anticipation of cold, fluffy powder snow.

  Image 1: Our program assistant, Ben Rossetter, enjoying some powder snow. Photo: Benjamin Glatz

Image 1: Our program assistant, Ben Rossetter, enjoying some powder snow. Photo: Benjamin Glatz

As a science education organization, we can’t help but ask: how do skis work?  How is a flat plank made of wood and metal able to so efficiently turn its human passenger while gliding across snow?

   
  
   
   
    
      
     
       Image 2: A
    parabolic ski shape.   
     
      
    
   
    
  
    
  
   
   
    
      
     
       Image 2: A
    parabolic ski shape.   
     
      
    
   
    
  
   A parabolic ski shape

A parabolic ski shape

Modern skis are built with a parabolic shape, and resemble an hourglass.  They are wide at the tip, narrow in the middle, and wide at the base. If a ski is standing still, it can’t do anything other than hold up the skier.  However, if the skier adds forward momentum and tilts the ski on end, the ski can turn.  The weight of the skier presses down on the middle of the ski.  When the ski is tilted on its edge, the middle of the ski bends down, so the whole edge of the ski is in contact with the snow.  In this position, the ski creates an arc, mimicking part of a circle.  The ski then follows the path of the circle, turning the skier, until the skier moves off the edge.  This type of turn is called “carving,” and is how ski racers are able to go so fast. It is a very efficient and fast way to turn a ski.

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There is another type of turn called “skidding.”  This is when the ski is set on edge, but instead of carving, the slides sideways over the snow.  The skid deflects against the snow, and allows the skier a little more control, though it is slower.

Now that we understand the science behind it all, let's hit the slopes! Happy skiing and boarding!  Enjoy your winter break and stay safe out there.


Image 3: Tracks from carving skis.  Photo: Chianti (CC BY 3.0)