The powder's perfect. All around snowboarders are shredding their way down the mountains and carving turns in the snow. Everything is going great until Steve catches an edge and face plants...and then, then it turns ugly. (Fact: There's no such thing as a pretty fall in snowboarding.)
So, what happened? How did Snowboard Steve go from kick flips to being the snow equivalent of a lawn ornament? Well, it all begins with friction.
Friction is the force that opposes movement when two things are in contact. It's constantly at work in the world and is what keeps things from sliding. So, in order to even begin to slide down the slopes, snowboarders must overcome limiting friction, the friction on an object just before it starts moving. As the board moves, the friction associated with motion, a.k.a. the sliding friction, transforms the energy of motion into heat.
Did you know? When it's cold, people use friction to warm their hands. By rubbing their hands they use friction to generate heat!
The heat melts the snow so that there is a thin layer of water between the board and the snow on which the board coasts. Basically snowboarding is just one loooong slide!
So, how does someone keep sliding down a mountain when friction is constantly at work? Cut out the excess friction! To reduce friction people wax their boards which effectively works like oil on a pan to prevent the board from 'sticking' to the snow. When someone carves a turn by using the edge of the board to go down the mountain, they are reducing friction by limiting contact between the board and the snow.
Well, if friction opposes motion, how did Steve overcome it in the first place? Besides muscle power (a force in and of itself) snowboarders rely on the force of gravity. Gravity is the attraction between two objects (kind of like Steve's face and the snow). The Earth, as a result of its giant size, constantly exerts a gravitational pull. That's what keeps everything from flying off the planet!
Did you know?The Earth's gravity is so great that even at a distance of 384,301 kilometers it still is what keeps the moon in orbit!
Gravity also has a lot to do with balance. An object's center of gravity is the point where the weight of the object is evenly distributed. It's important for a snowboarder to keep his/her center of gravity over the edge that is in contact with the snow.
That's why people shred, shifting their weight to move the board from one edge to another, in order to keep their center of gravity over the riding edge.
Did you know? The same principles involved in snowboarding can be applied to ice skating - thin blades limit surface area while generating enough heat through friction to melt the ice and to make a thin layer of water to on which to slide. Gravity plays its part by allowing one whole human to stand up on those two tiny blades.
So remember, the physics of snowboarding are simple: keep your center of gravity above the riding edge and don't get caught by friction. (pssst, pass it on to Steve once he recovers from his wipe out.)
Canadian Snowboard Federation
The ABCs of Snowboarding
Physics and Astronomy Online: Snowboarding