Friction and snow

1. Aug 22, 2007

Mash

Hi,

I am trying to make a simply model of a snowboarder for a computer game.

I have implemented basic friction, he slows and comes to a stop when the acceleration force is less than the frictional force.

I am now puzzled as how friction changes when the snowboarder turns. As the snowboarder turns 90 degrees on a hill, he comes to a complete stop also, and does not slide down the hill sideways. Why is this? What prevents a snowboarder from snowboarding uphill?

Any help/discussion would be handy

Mash

2. Aug 22, 2007

cesiumfrog

The acceleration is just gravity (not the person, hence snowboarders go downhill). The key concept would be that the coefficient of friction is different in orthogonal directions. A ski is deliberately shaped to slide smoothly over snow in one direction, but plough to a stop in the the other.

(This really only belongs in the general physics forum, what's with the double-posting?)

Last edited: Aug 22, 2007
3. Aug 22, 2007

Staff: Mentor

A snowboarder can most certainly snowboard uphill in a turn until they run out of momentum. What prevents it when they stop is that they let the board slide instead of biting and carving out the turn.

4. Aug 23, 2007

Mash

Ahhh, so the coefficient changes... that makes things simpler. Oh yes, I thought that it should have been in classical physics (mechanics) after i already posted under general. Sorry bout that.

Would it be fair to say that the coefficient increases as the angle between the acceleration and the direction of the snowboarder increases?

5. Aug 23, 2007

Mash

Oh right. Is it possible to do a complete 360 degree turn going up the hill then back down if you had enough speed? Or is there some sort of bound on how far you can travel uphill...

6. Aug 23, 2007

cesiumfrog

No. What matters is the angle between the snowboard and its velocity. You would have sliding friction along one axis, and normally static friction along the other (it works like a roller-skate). And actually it seems to be that axis that moves due to board deformation as the person leans, to steer. You know, one could do a snowboarding simulation that begins right from the design (and characterisation) of the board..