So if you jump from the same height on skis or just in your shoes regardless of the landing (flat or sloped) the impact to your body will be greater in shoes because greater ability of skis to dissapate the energy of the impact. It works in two ways.
1. The ski. Most skis are cambered, this acts a shock obsorber (think leaf springs on a truck) this helps disappate energy. Energy also gets disappated through the tip and tail of the skis by way of vibrations which are induced from the force of the impact. With shoes all you have is thin rubber sole to obsorb the impact.
2. Because skis have a realitvly low co-efficent of friction, they will slide and thus incase the duration of the impact event. Where as with shoes you can only hope to increase this duration by rolling out. Say you jump off a 10 foot high roof, on skis you land and slide say 8-10 feet, in shoes you can only roll 4-5. In both cases the kinetic force of the fall will be the same, but with the skis on the force has twice the distances to dissapate in.
I very much disagree with you.
1. The camber of the skis will have a noticable effect. Say you have 1 inch of camber, thats like having a shock absorber with once ince of travel, it makes a difference. Good example try poping with cambered skis then try with flat or reversse camber skis. A real world application of this is leaf-spring suspension systems, which you can easily see on any pick-up truck. So if your saying thats wrong, you also saying a suspension system used in vehicles (while not the best) is completly ineffective.
2. Yes skis are elastic which is why they vibrate, but what are vibrations, well they are a form of energy. So when the impact occures if the impact energy is transformed into vibrations there is a greater dissapation of froce. Even the stiffness of ski matters, a stiffer ski will have a frequency and produce shorter wave length, where as a not so stiff ski will have a lower frequncy and produce a longer wave length. The reason this matters is because transfering the energy of the impact is all about making the impact last as long as possible over the greatest distance possible. So a loose ski vibrating with a longer wave length disperce the impact over more time and a longer distance then a stiff ski would.
3. I want to call you an idiot...so I am, you're an idiot. Duration of the impact is a huge part of how a collision is dissapated, that and the distance the impact occures over. These two factors have a direct result in how much force is transfered from one object to another. I think that teach that in grade 10 physics. An example of this is a down sloped landing. Why does a steep angled landing allow you while your sking to dissapate force? Because of the way it transfers your downward motion into forward mortion. But how does it do that? It does it because the time inwhich the impact takes place is longer as well as it takes place over a longer distance. Thus indication that the duration of the impact has quite a bit to do with it.