The physics of skiing and snowboarding

In an earlier article, we talked about the physics of surfing and water skiing. Now it’s time to talk about the physics of winter sports.

When going down the mountain

Skiing and snowboarding share the same physics principles: a person stands on their board, and their weight is distributed across the board. This helps you avoid falling when there is loose powder, and makes it possible to get down the slope quickly.

The main force that acts on skiers and snowboarders is gravity. To keep their balance, a person only has to turn and slow down in time. Gravity does the rest—acceleration occurs, and the speed of the descent increases.

Gravity is counteracted by the force of friction: the flat surface of snowboards and skis glides well on snow, but microscopic irregularities still create friction, slowing down movement, and generating heat, including heat in the form of light particles, or photons.

The green arrow represents gravity, the blue arrow represents air resistance, and the red arrow represents friction. Photo: k2_104

The energy of these photons is not enough to be seen by the human eye. But the heat from them, when added to the heat from contact with the already heated molecules of the board, is enough to slightly melt the snow. This creates a thin layer of liquid water, which improves glide. The effect is especially noticeable in extreme cold conditions, when the snow melts much less. If there is too little water, the board doesn’t glide as fast.

Also, the force of gravity is hindered by air resistance. Since the board is directed towards the oncoming air with its sharp end, which reduces the resistance of the atmosphere, the entire impact of resistance is taken on by the body of the skier or snowboarder. Therefore, the more streamlined a person’s posture and clothing is, the faster they can move.

Turning

Turning on skis and snowboards is helped by the force of friction. The person leans in the direction of the turn, and their center of gravity is outside of the board—as a result, one edge of the board goes deeper into the snow, and the friction with the snow increases, while the other edge rises into the air, decreasing friction. Because of the difference in friction, and the shift in the center of the mass, the board turns.

However, turning is prevented by centrifugal force. You can also see this phenomenon if, for example, you hold hands with another person and spin: as your speed increases, you are pulled further and further away from each other. More precisely—from the center of your shared axis of rotation, i.e. from the point where you are holding hands.

This is because all physical bodies tend to maintain their direction of motion—that is, they move because of inertia—and rotation prevents this. When you turn on skis, or on a snowboard, the motion also has a center, and you move around this center. But a second before you start to turn, you are moving in the other direction, forward, and you are still being pulled in that direction by inertia.

This force, which tends to push snowboarders and skiers to the side when they are turning, is compensated for by gravity and friction—if using the correct technique, the board clings to the snow enough so that the person is not carried in the opposite direction, and does not fall.

The centrifugal force, in turn, compensates for gravity—so that a person does not fall to the side when they lean into the turn—just as a cyclist does not fall when they have accelerated enough to easily keep their balance on two wheels.

The black dotted line shows the approximate path of the turn, and the red circle shows the center of the turn. The blue arrow is the centrifugal force, and the red arrow is the approximate direction of the friction, which now slows the skier down, slightly to the side, instead of the front. Photo: Volker Meyer

What’s different between snowboarding and skiing

Despite all the similarities, there are still some differences between the physics of the two sports. Skiing was originally invented as a means of transportation over snow, not as a recreational activity. Snowboarding seems simpler and more comfortable, because it was designed for fun going down the slope.

The skier leans forward while moving, whereas the snowboarder leans slightly backward, which is intuitively more comfortable. But it’s easier for a skier to keep their center of gravity between the two skis even on a turn, while a snowboarder has to constantly worry about not falling, because of the significant shift of the center of gravity to one side.

Photo: Digital Vision/Getty Images

Because snowboarders keep all their weight on one wide board, rather than spreading it across two narrow skis, skiers have better maneuverability and speed.

If we take the world records for speed, at the beginning of 2024, skiers have reached 255 kilometers per hour, while snowboarders have only reached 211kph. As a result, skiers jump higher and farther—11.7 meters in height, and 253 meters in length (a quarter kilometer in total!). In comparison, snowboarders were able to jump 10.6 meters high, and only 57 meters long.

Snowboarding, however, is considered safer. Because all four of a skier’s limbs move independently, the potential for injury is still higher than that of snowboarders if they lose control of their movement.

Recommendations for the ideal temperature for skiing vary widely. The most important thing is that the snow is dense, so −1°C to −18°C is usually advised.

Text: Jason Bright, a journalist, and a traveler

Cover photo: Ethan Walsweer / Unsplash