The Physics of Skiing

physics of skiingLast month I made a connection between intermediate skiing and geometry.  This applies to advanced skiers and to take it a step further, I’ll add physics to the mix.

There are two ways to put your skis on edge. The first method, inclination, uses the whole body. Angulation, the second method, creates angles by using our hips and knees joints.

When skiing at speed we can tip our whole body relying on centrifugal force to hold us up. These banked type turns can be fun in a cruising type mode but will not allow for very good edge hold as the edge angle created can only be as large as the amount of body tip.

When we tip using our hip joint and keep our upper body upright so that our shoulders are level to the horizon, we can create a much larger edge angle. In this way we utilize our most powerful joint which is surrounded by a web of powerful muscle.

This allows us to resist the forces that want to both tip us up hill while pulling us off our round turn shape and ultimately hold a better edge.  Angulation in your knees should only be used to fine tune things as those joints are much weaker and fragile and offer less range of motion than our hips.

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Skiing Geometry for Intermediates

Last month I used the ABC’s to teach children how to shape their turns for speed control. This month I’ll try to help intermediates get out of the rut and make better turns. To suit the higher ability level, I’ve moved the analogy from grade school ABC’s to high school Geometry.

skiing geometry

When I work with intermediates, I try to get them to think of their boots as being square instead rounded. In past we’d tell students move your shins directly forward into the front of the boot. Now, with modern technique we want to move those shins diagonally into the corner of our imaginary square boot tops.

If you tip both shins in the same plane into the corner of the square box (top of your boots) the skis will roll up on edge. Start by tipping your shins into the uphill corner of the square on the bottom half turns (after the apex). Try a gentle green trail and notice how your skis respond. As you gain confidence with this move try to gradually push toward the corner earlier in the turn. Not only are the skis parallel, but the planes that the shins tip in are parallel.  This leads to the leg angles that are parallel too.

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The ABC’s of Skiing With Kids

I recently taught a Play-and-Ski lesson for two 5-year old kids. After watching them ski I asked one little girl how she learned to slow down. I got the answer I anticipated: “I just make a bigger pizza.”

ZZ using a small wedge and turn shape to control his speed

From the very early stages skiers learn that a bigger wedge increases resistance to the snow. Many young kids take this knowledge and apply it to all their turns or anytime they need to slow or stop. Occasionally an inexperienced instructor or parent reinforces this big pizza idea and it firmly takes hold. The bigger wedge moves their center of mass farther back putting them farther into the back seat making all the skiing skills harder to apply.

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