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Last Updated9 June 2023
Ski instructors should not underestimate the importance of understanding the principles that make a ski speed up, slow down, or change direction. This chapter defines some of these basic concepts and looks at how they are applied. It explains the forces acting on a skier when standing still, then in
 a straight run, to demonstrate the basic forces that set skiers into motion, speeds them up and slows them down. Finally it studies the changes in these forces when a skier turns.

Ski Interaction Angles

When a beginner skier starts turning or a more advanced skier accelerates down a blue slope making medium radius turns, the forces acting on them increase. In both instances, the skier experiences this increase in force as an increase in pressure this pressure will be felt by the skier under their foot as it is the closest body part to the ski.

At a fundamental level learning to ski is learning to harness and manage
 the forces acting upon the skier and the pressure those forces create. As skiers develop their skills and situational understanding they will develop a desire to go faster and to steeper terrain. This will result in the skier experiencing greater forces acting upon them in the form of greater pressure. The external factors that impact the forces acting on a skier are the skier’s speed of travel, the snow conditions and the steepness of the slope. The internal factors that impact the forces acting on a skier are the skier’s ability to coordinate the four movements of skiing. The more ski instructors understand about the forces that are at work when skiing, the better equipped they will be to choose skill areas that will create successful outcomes.

The Ski Interaction Angles

The ski interaction angles are the terms used to describe how the skis interact with the snow. These terms and concepts have been adapted from Ron LeMaster’s Ultimate Skiing (2009).

The ski interaction angles are:

Edge Angle
The angle between the bottom of the ski and the surface of the snow. This affects how much the ski bends in a turn and determines the resulting radius and shape of the turn.

Steering Angle
The angle between your direction of travel and the direction in which the ski is pointed. This determines how much friction acts on the ski; this slows the ski down and impacts how tight the ski can turn. Also, every ski has a built in steering angle. This angle is also referred to as the ski’s side cut.

Platform Angle
Platform angle determines whether a ski slips and skids, or carves and holds in the snow. For the ski to hold and carve the force being applied to the inside edge and/or base of the ski as it penetrates the snow must be at 90 degrees or less than the reaction force pushing back on the ski from the snow. For the ski to skid and slide sideways the force being applied to the inside edge and/or base of the ski as it penetrates the snow must be greater than 90 degrees to the reaction force pushing back on the ski from the snow.

Recommended reading for further studies:

  • Ultimate Skiing – Ron LeMaster, 2009 Human Kinetics
  • Skiing Mechanics – John Howe, 1983 Poudre Press
  • The Physics of Skiing; Skiing at the Triple Point – David A. Lind and 
Scott P. Sanders, 2004 Springer