Ski Energy

The Physics of Skiing is Newton's Physics and not Einstein's
The Physics of Skiing is Newton's Physics and not Einstein's

Energy is a term we hear about quite a bit, we have a general notion of what it means, but unless we remember our basic physics we have usually have less than a precise understanding of energy.

We know our cars need energy to move, we know we need energy to heat our food, to light our nights, and to perform other useful tasks. However, let us focus on mechanical energy which is basically the energy objects have via their motion.

In a non-mathematical way, energy is the ability to do work which is to cause an object to alter its state of motion or to move it. Simple example, move a 1 kg brick one meter up in the air and you have done work. It is important that mass is moved, if you push against a wall with all of your might, but the wall does not move, no work is done.

The other thing you need to keep in mind is that energy is neither created nor destroyed it simply changes from one form into another. The trick is to being able to capture and make the energy to do useful work.

So in order to ski you need energy. How do you get that? Gravity supplies that, but the trick is to get up the hill and that requires…energy. Quite simply we ride the chairlift, take the towrope, or t-bars to the top of the run, now we are loaded with potential energy and are ready to work. Quite obviously the chairlift gets it energy from some other source of which you are familiar with. There is no free lunch here.

So now you stand atop the ski run full of energy, what happens to that energy? As you propel yourself down the ski trail it converts from potential energy to kinetic energy — energy due to motion. Plus, some of the energy converts to heat, sound, and some is transferred to the snow (especially if you skid-ski, or snowplow) and pushes the snow around. The energy causes you to move down the hill.

Sir Isaac Newton the Father of Ski Physics
Sir Isaac Newton the Father of Ski Physics
If you schuss the hill nearly all of your original potential energy converts to speed (however, there are other forces in play resisting your tendency to increase speed) and your burn through the energy much quicker (increased power). How much energy do you have? Your energy is dependent on your mass and your speed: E= ½M*V2 That is, if your mass is 100 kilograms (ie you weigh 220 pounds) and are fskiing down the run at 18 m/sec (40 mph) your energy would be ½*(100*182)= 16,200 joules (3.9 food-calories). What if you were skiing 9 m/sec (20 mph), what would your energy be? It would not be 8,100 joules, but 4,050 joules, remember the velocity is squared (the energy to make your car go from 25 mph to 55 mph is a bit of 4x the energy it has at 25 mph).

Now not all energy is converted to speed. Some is used to overcome resistive forces such as friction and wind resistance, some is used to assist in turning (changing your motion), and maybe a lot of energy is used to send your gear flying and you tumbling down! Those other uses of energy rob you of potential energy you could exchange for speed. So to maximize speed you need to minimize friction between your skis and the snow, minimize wind resistance between the air and your body, and making your turns as efficient as possible.

To maximize your speed: carve your turns, keep your bases smooth and waxed for the conditions, wear a race suit and hold an aerodynamic tuck.

Good Stuff!

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