Originally Posted by clink83
Eh, your 100% wrong. The coefficient of drag ranges from 0-1, putting on speed suit will only change it by maby .1-2. That's a marginal increase compared to weight. It all comes down to f=ma. This should be readily apparent on the ski slope. At 200lbs on a snowboard I would be faster than most normal sized skiers on flats.
If aero was so important with ski racing they woouldnt be skiing with uncovered boots. In bike racing wearing shoe covers will shave a couple seconds off a 50k time trial. 3k aero rims will only shave a couple seconds too, and an aero helmet..a couple seconds. That's on a 50k bike ride, not a short 1-2 mile ski run. Aero is wayyyy overrated.
There is only one force driving a skier down the hill when skiing. That force is gravity. Because gravity is essentially acting straight down, and a skier is on a slope (or inclined plane) the vector component acting on the skier is equal to mg*Sinθ, m being mass, g being acceleration due to gravity, and θ being the slope angle. The rate at which this object will accelerate down that slope (the primary factor in determining how fast that skier will go) will be based on F=ma. F is the vector component I just mentioned (mg*Sinθ). m is the mass of the skier, and a is the acceleration that the skier will experience. We have already seen that F=mg*Sinθ so we can substitute mg*Sinθ in and we have mg*Sinθ=ma. Since we have m on both sides, we divide each side by m canceling out the effects of mass. Considering that Weight = mass * acceleration due to gravity, if mass is not a factor, neither is weight. Like I said "Weight has nothing to do with it."
If we were talking about carrying speed over flat ground while decelerating from resistive force, weight would make a difference, but in terms of two objects sliding down a hill, it makes no difference.
When we consider wind resistance, once again its a question of F=ma. F in this case is the resisting force created by the air/wind. More weight=more mass, so if we increase m, it will require a greater force to decrease the acceleration of a skier. Assuming two skiers of the same shape and size, but different weights, the wind resistance will be equal. So F is the same for both. We can see that ma=F=2m*0.5a So if you double the mass, the opposing acceleration is cut in half. If you were to increase the mass by 10%, the opposing acceleration would be reduced by one tenth.
Now this is where it gets interesting. Typically a person's volume and therefore cross sectional area increases with their mass. Assuming two skiers of equal density, with different masses, the differences pretty much cancel each other out. If the densities of the two skiers are significantly different, there will be a difference in cross sectional area that can either negate or intensify the effects of wind resistance discussed above. In other words, high density would be low surface area with lots of mass (a lead broomstick), and low density would have high surface area with little mass (a spread out bed sheet). So yes weight can make some difference in terms of a skiers reaction to wind resistance.
This discussion really started over the comment :
Originally Posted by clink83
They would have the same speed. 30mph is 30mph. They would accelate differently though. The heavier skier would accelerate faster than the light skier because weight is a bigger factor than the coefficent of drag.
The difference between speed and acceleration is a concept lost on many though.
And as I said, the acceleration of a skier has nothing to do with the weight.
Tog brought up momentum, and in a way he is correct. As I demonstrated above more weight is less impacted by wind resistance, which is essentially the result of inertia, which is closely tied to momentum.