Originally Posted by justanotherskipro
You guys are so off base here, review the following before responding though. Is the opinion I'm sharing here valid?
"Because there are so many misconceptions about mechanics that enter technical discussions, I though it beneficial to address the most common ones encountered over the years. A major reason for misconception is not clearly understanding the concept of cause and effect
. When discussing the mechanics of human motion, this concept is particularly important. You want to control and guide your motion, so you need to understand that you are continuously interacting with the forces that exist between you and the environment. What you have under direct control are the actions you can take with your body not
forces between the equipment and the snow. So snow skiing is really the act manipulating the way the ski/snow and pole/snow reaction
forces act on your skis and poles. Of course, ski/snow interactions are a two way street. In addition to providing the means to acheive motion that you desire, these interactions are the major source of disturbances that you must counteract.
Another problem area is in developing a clear understanding of what centrifugal force is, as well as understanding the concept of a centripetal force. In fact, many difficulties in thinking about skiing mechanics can be traced to a confusion about the true nature of forces and the need to seperate external, motive forces from inertial forces. The key is that external motive forces cause changes in motion, inertial forces are the result...
...The principle difficuly with the notion of centripetal force is that one may bring this concept into the discussion in addition to the ski/snow interaction forces as if centripital force were something different from the radial (inward acting
) component of the ski/snow interaction force...
...If we consider the example of running into a stationary object we can see how this works. Some motive force was required to get you moving at a high rate of speed to impart large momentum. Now, when you run into the object, to stop you (remove all the momentum) the object must be capable of generating a large force. Your momentum did not create the force...
...what we do sense, whether standing on the bathroom scales or moving on a pair of skis is the reaction force between our bodies and whatever is supporting them...
...When you stand still, the scale reads your weight and we know from Newton's first law this is really the measure of the reaction
force in the scale to your weight: The action is your weight and the reaction
is the force exerted by the springs in the scales. Then drop suddenly and have a friend observe the reading on the scales. As long as you are dropping (accelerating downward) the scale reads less than your weight. This is as it should be since to accelerate downward, the resultant of the force of gravity acting down must be greater than the force exerted by the springs of the scale acting upward. Put it another way, the scale needs to exert less pressure than your weight because it doesn't have to keep you from moving downward. Unfortunately, this moment is brief indeed as you cannot "fall" very far! When you tense your muscles and stop your body from dropping, the scale will momentarily register a reaction
force greater than your weight. The reason is that now the springs in the scale are decelerating
you (stopping your body from falling) and this requires force greater than just your weight. The reaction
force must equal your weight plus the mass times acceleration part, which is now in the opposite direction. As soon as you have stopped moving, the reading on the scales returns to your weight because the acceleration now is zero. Change the rate at which you perform these movements and observe the changes in the scale reading as part of your experimentation...
...This situation is entirely analogous to the amount of "rebound" you get from your skis on hard snow verses powder."