Quinn BehnkeWRIT 340

Illumin Article4/2/12

The Art of Flight©: The Physics of Freestyle Snowboarding

KeywordsPhysics, sports & recreation, lifestyle

Multimedia http://www.youtube.com/watch?v=072fU3Yjgq0

BioQuinn is a senior in Mechanical Engineering at the University of Southern California. He is a Colorado native and an avid snowboarder. He is a member of the USC Ski and Snowboard Team.

Abstract

Freestyle snowboarding is an amazing sport to watch. But in order to understand how the athletes are performing their gravity-defying tricks, one must grasp the basic laws of physics. The effects of gravity, energy and momentum have huge implications for the ability of freestyle tricks to be performed. Despite the ease displayed by the riders, an intuitive knowledge of these laws must be held in order to successfully complete the difficult maneuvers seen in freestyle competition.

Introduction

Anyone who has watched the Winter Olympics in the past decade will have witnessed the

sport of snowboarding. Riders compete in different events that are judged on speed, style, air and

tricks. Freestyle snowboarding has become a popular form of the sport and is comprised of

several aspects. The riders perform dizzying maneuvers off of man-made and natural features

that require exceptional technical discipline. Witnessing the athletic ability of these riders

spinning and jumping in competition says a lot about the knowledge they possess. In these

competitions, riders push the limits of physics using orchestrated techniques and new material

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technologies. Despite the impressive performances seen in both the Olympics and X-Games, the

basics behind the tricks are quite simple and are governed by the physical laws of the universe.

History

Although there is no official record of who invented the snowboard, backyard enthusiasts

began experimenting with the idea of snowboarding in the 1960s [1]. It wasn’t until 1977 when

the first snowboard was constructed and sold by a newly formed company, Burton Snowboards

[2]. The founder, Jake Burton Carpenter, began experimenting with the existing surfboard

technology to create a revolutionary board that would allow people to surf the snow. Snowboards

initially began as rounded planks of wood with a single nose-rope to direct the path of travel, and

later straps were developed to hold a rider’s feet in place [2]. From that moment on, the

snowboard movement developed quickly, as surfers and skateboarders alike began to invest in

this new sport. The sport began to invade local ski resorts in the 1970s, instigating the conflict

between boarders and skiers that still exists today. Despite the initial displeasure of the skiers, ski

resorts began accepting snowboarders on their slopes, recognizing the potential for increased

revenues [1]. Over the years, competitions were created to judge the ability of riders in different

areas.

The X-Games is one major competition that hosts extreme sports, with the Winter X-

Games focusing intently on snowboarding and skiing. In both the X-Games and the Olympics,

freestyle snowboard progression has been unstoppable and riders are traveling higher and farther

than ever before. When watching the riders perform the dizzying maneuvers, there is an under

appreciation for the physics that lies behind the different tricks. The two main freestyle events

are slopestyle and halfpipe. Slopestyle involves a course riddled with various jumps and rail

features that allow riders to be creative in performing tricks. Halfpipe events involve riders

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traveling up the sides of a circular snow “pipe” and jumping above the walls. Figure 1 below

shows a side by side comparison of a halfpipe and slopestyle course.

X-Games

Figure 1. Slopestyle course and halfpipe to the left and right, respectively

In performing these tricks, the competitors possess a respect and knowledge of various topics in

physics. Laws of gravity, momentum, friction, energy and acceleration account for the ability of

the rider to perform the increasingly difficult tricks seen in these competitions.

Physics

The most significant law behind this sport is that of gravity. It causes a rider to accelerate

on the snow and gain speed in order to go off of jumps or grind down rails. When dealing with

jumps, many aspects are important in ensuring the safety of the rider as well as the feasibility of

certain tricks. The acceleration built up by a rider as they approach a jump allows them to

overcome gravity and fly through the air, until gravity takes over and pulls them back to the

ground. Judging the correct speed at which to hit a jump is no easy task. It involves determining

the speed required to clear the jump and land safely on the other side, as well as the momentum

required to successfully spin one’s body around. A rider will crouch during the approach to the

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jump so they can gain the necessary speed. Conservation of energy, which is governed by the

equilibrium of kinetic energy and potential energy, explains why riders are able to clear jumps

[3]. The kinetic energy of the rider as he approaches the jump is related to their speed. The

equivalent potential energy is related to the force of gravity and the height of the rider above the

ground. This means that the faster one travels, the higher and farther they will travel. This is

important as a critical speed must be determined in order to gain enough air to successfully clear

the jump without over- or undershooting the landing.

Many aerial tricks involve the rider rotating a given number of degrees in the air. Angular

momentum governs these rotations and determines how much spin is achieved off of a jump.

This can be pictured by visualizing an ice skater spinning in place. If the skater brings their arms

closer to their body, their angular momentum will increase causing them to spin faster. As their

arms are extended, the spinning begins to slow. This concept is readily visible in freestyle

snowboarding, as a rider will crouch and the tuck during a spin to conserve angular momentum.

To initiate the spin, a rider will twist their body sharply at the takeoff, which gives them the

momentum to rotate around. In the air, a grab is incorporated into the spin to help the rider

maintain momentum and stay balanced in order to complete the spin. This technique can be seen

in Figure 2, where the rider performs a 540° spin with a grab. As the rider nears the ground, they

will outstretch their arms to reduce the speed of rotation so a straight and stable landing can be

achieved [4].

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Figure 2. Photo sequence of a snowboarder spinning off a jump

Friction and momentum are very important physical aspects in the sport. They govern a

rider’s speed as they travel downhill and throughout the terrain park. A certain amount of friction

is necessary for a snowboarder to maintain control; however, too much friction can reduce the

rider’s speed below the necessary amount to jump successfully. This is very important in an area

called jibbing. Jibbing is a term coined to describe tricks involving rails and boxes, which are

popular features in freestyle snowboarding. The purpose is to jump onto the rail and slide down

its length and then jump off. The rider’s momentum is what carries them down the rail without

losing speed. Too much friction will cause the rider to slow down and stop on the rail, forcing

them to fall. Negligible friction is ideal as this allows the rider to slide down the length of the rail

without losing speed and falling off [4]. Friction is reduced on a snowboard by waxing the

bottom and dulling the metal edges around the board. Wax reducing the sticking sensation that

the snow causes against the board when riding. Dulling the edges of the board makes it easier to

grind on a rail and reduces the chance of catching an edge and falling. More advanced riders

incorporate spins both onto and off of rails, which is a function of angular momentum. The idea

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DeviantArt

remains the same as with jumping, where a certain amount of angular force will cause the rider

to begin spinning until the momentum is reduced and the rotation stops. Figure 3 below shows a

rider spinning onto a rail and grinding down its length.

Figure 3. Photo sequence of a snowboarder spinning onto a box

Board Design

In order to perform the many difficult maneuvers, freestyle snowboards are designed to

work with physics to make such tricks possible. Snowboard construction is a detailed process

that involves selecting the appropriate materials for the inner layers of the board and determining

the shape. The first goal is to make the board as light as possible, as this decreases the overall

weight that the rider must carry through the air. This in turn affects the downhill and rotation

speed. A lighter board allows a rider to spin faster and jump higher because the force of gravity

is smaller. The problem with creating lighter boards is the reduction of strength. The most

popular materials for current boards include carbon and some wood grains, as they have a high

strength to weight ratio [5].

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Transworld Snowboarding

The overall shape of a freestyle snowboard is symmetrical, or commonly referred to as

“twin-tip”. This means the nose and tail of the board are the exact same, which allows it to be

ridden in either direction. This is important because riders can ride backwards, or switch,

allowing for different spins to be achieved. Rotations such as 180°, 540° and 900° require the

rider to either take off or land switch. Freestyle boards are typically softer, making them more

flexible and forgiving on rails. The softer flex means that riders can press their boards, which

involves balancing on the nose or tail of the board, respectively. To perform a nose-press, the

snowboarder will lean forward until all of their weight is over their front foot and then balance

on this foot. This motion cause the tail of the board to rise off of the snow and the rider will be

moving downhill while balancing on their front foot. The same motion can be repeated for a tail-

press, but the rider instead balances on their rear foot. Another important aspect is the board’s

side cut and overall length. The side cut of a board determines how quickly a rider can change

direction by turning. A small side cut means quicker turns, which is important in freestyle for

boarders to alter their approach to the feature. The overall length of freestyle boards is shorter

than all-mountain ones, as this reduces weight and makes tricks easier to perform. Figure 3

shows some typical definitions of snowboard dimensions.

Figure 3. Board dimension guide showing sidecut with nose and tail.

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Mechanics of Sport

The effective edge is the edge length that is in contact with the ground when making a turn. This

is determined based on the overall length of the board, which is sized for the specific rider’s

height. The camber of a board described the arch of the board when laid onto the snow. Some

new boards have a reverse-camber, or rocker, shape. This means that the entire base of the board

does not rest on the snow surface; the nose and tail are arched upwards and do not contact the

snow. This makes it easier to initiate spins off of jumps and reduces the risk of catching an edge

when riding.

Future

With the continued improvements in snowboard technology, competitors are able to spin

faster and jump farther than was ever thought possible. The world’s longest jump record is

currently held by Norway’s Mads Jonsson, which was set in 2005 at a mind-boggling distance of

187 ft [6]. As riders continue to push the limits of snowboarding and themselves, this record

could be broken in the near future. Snowboard design has made large advancements in recent

years, helping riders to perform these more difficult tricks. There has also been research into

different flex designs and ideas for other materials. Further material and design testing will allow

boards to become stronger and lighter than ever before. Other undeveloped ideas could again

alter freestyle snowboarding forever. Despite the increased difficulty of tricks in today’s

competitions, they same basic laws of physics govern the movements in freestyle snowboarding.

A rider must understand these laws and use the correct methods to use physics to their

advantage.

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References

1. “Snowboard Equipment and History.” Internet: http://www.olympic.org/snowboard-equipment-and-history. [2012]

2. “Company History.” Burton Snowboards [On-line]. Internet: http://www.burton.com/on/ demandware. store/Sites-Burton_US-Site/default/Company-History. [2012]

3. L. Kramer. University Physics. San Fransisco, CA: Pearson Education, 2008, pp. 47-179.

4. F. Normani. (2009) “The Physics of Snowboarding.” Internet: http://www.real-world-physics-problems.com/physics-of-snowboarding.html [2012]

5. “Snowboard Construction.” Internet: http://www.mechanicsofsport.com/snowboarding/ equipment/snowboards/snowboard_construction.html. [2011]

6. “Snowboarding World Records.” Internet: http://whitelines.mpora.com/features/ debate/snowboarding-world-records-frontside-7-issue-97.html. [9/2011]

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