Question

1. Advanced skiers turn by sliding the backs of their skis across the snow. Since the fronts of their skis don’t move much, the skis end up pointed in a new direction.

a. The amount of sideways force that a skier must exert on the skis to slide them sideways is proportional to how hard the skis press down on the snow beneath them. Why?

b. Less skilled skiers sometimes turn without unweighting—they push their skis sideways so hard that the skis slide anyway. This technique is exhausting. Why does it require so much work?

c. Why is wax used on skis? Why wouldn’t WD-40 work as well as the wax? What is in WD-40?

Answer 1

a) There is friction that is produced when skies slide across the snow. This sliding friction is proportional to the forces pressing the two surfaces together. This force increases as the force pushing the two surfaces together increases.

b) Without unweighting, the force of sliding friction is large. Since the work done against sliding friction is the product of the force needed to slide the skis times the distance of the slide, having a large sliding friction force to overcome makes the work required to slide the skis sideways large. This is because the more force pressing the skis against the snow, the larger the force of sliding friction that opposes the slide. Since the skier must overcome that sliding friction force in doing the work required to turn the skis, increasing the sliding friction force increases the work done.

c) WD40 works as a base cleaner/wax remover, but it’s bad for the ski pours. You should let the ski dry and then wax it immediately after you used wd40. in terms of wax, its only good for like 2 runs at most and its fast b/c it sucks the chemicals out of the snow. Watch your bases turn black and get ruined.