September 2016 Language of Physics Remembering Coombs Blood Types Parks Centennial Skating and Skiing Stress 5-pt Sidecut Skis 1 Page 2 Peak Performance, September 2016 Photo on the Summit On the cover photo: Doug Coombs takes on the mighty Corbet’s Couloir, often called the “world’s gnarliest marked run.” Classic photo by Bob Woodall – Focus Productions. See more about Doug Coombs on page 6. Long time ago, Barry Corbet, a ski instructor at the Jackson Hole Ski Resort in Wyoming, spotted the narrow ribbon of snow between the rock faces and said “one day that’s going to be skied…”, with the first descent by patroller Lonnie Ball in 1967. But, I don’t think he said that this will be a marked ski slope. Advice for the first timers going down Corbet’s: stay left, drop, instant hard right, and wrestle back control before the cliff face on the opposite side is fast upon you. Jackson Hole’s Aerial Tram will take you up 4,139 vertical feet in 9 minutes. It can hold up to 100 people plus an operator, and it can operate in 70 mph winds. 2 Peak Performance, September 2016 Page 3 Contents Page 4 Language of Physics Juris Vagners From the Top Page 6 Remembering Coombs By Witold Kosmala The Publisher and the Editor of Peak Performance Gazette Witold Kosmala PSIA-E Alpine, Level III Ski Instructor, Coach and Trainer mostly in NC K2 Ambassador Page 8 Parks Centennial Welcome all our new and returning readers to this 68th issue of Peak Performance Gazette. Our passion is National Parks Foundation skiing. This does not mean that every day of our lives we wish Page 9 Blood Types it was winter. It is not just wishing for deep pow conditions and bluebird skies. It is not just going to American Red Cross exotic ski areas or attending awesome camps or clinics. It is not just owning a good pair of skis or bindings. It is not the love of sliding or a rush it gives Page 11 Stress – Weight Gain us. The package is much larger than that. If our passion is skiing we must care about our world, and Witold Kosmala about each other, as we are part of it. We must not only care about physical, mental, and emotional health, but care about so many other things Page 12 Skating and Skiing – practically everything. Try naming one thing that does not affect skiers, and you will realize that that too is Witold Kosmala part of the ski world. We should care even about where the wax goes off of our boards. Seemingly everything is part of skiing – definitely not just ski Page 18 5-pt. Sidecut Skis technique. For this very reason, we try to balance our Peak Performance publications to include a variety of Witold Kosmala topics. For skiing, LIFE is definitely a must. There is no life without blood, and there is no synthetic blood. However, so many of us lost blood and needed more of it. The only place to get more blood (for now) is from another person. I know that without other people donating blood, I would not be here today. After my skiing accident 8 years ago, I was loosing blood quicker then they could pump more into me, and all that came from donors. I can’t thank those people enough for giving me LIFE. I wrote an article on donating blood in the March issue of Peak Performance Gazette. There is another article on blood on page 9 in this publication. I encourage you to donate. Let’s make a difference in the world one skier at a time. So, the ski season in the North America is around the corner. Are you prepared? Are you training and studying? Is your equipment ready to go? Are you motivated and mentally strong? Do you have a plan? It is good to see you reading this gazette. We hope that you will find it truly worth your while, just like all the previous issues. Don’t dismiss the old issues. They contain material which is still current. Hope you can look through the Article Index compiled by Gordon Carr of Sugar Mtn. NC. It can help you locate an article that you are looking for, or just see what sort of articles have been published. You can find it the same place where you can find all the issues of Peak Performance Gazette. Here are a number of ways to do that. Choose your favorite method. 3 Page 4 Peak Performance, September 2016 • Use the dropbox www.dropbox.com/sh/wjrz16pzrpho63i/PQr004dmUj • Go to the website www.peakperformancegazette.com • Look up the Facebook www.facebook.com/peakperformancegazette • Google search “Peak Performance Gazette” and see the first item. • Go to the bottom of my Appalachian State University (ASU) webpage www.mathsci.appstate.edu/~wak/ • Go to the ASU Library's webpage at www.library.appstate.edu. My hopes are that these gazettes will serve you as an outstanding reading material no matter what your calling is. Hopefully these publications will make your skiing passion grow even more, bring you awareness, improve your technique, take you on the hill more often and help you pass that next certification exam. Take a minute and write me at [email protected] and tell me what you think about these gazettes. Perhaps you would like to get involved and share your knowledge with other skiers. Write an article, share a photo, tell us about your unusual or funny experiences, send a donation. I would love to hear from you. If you like what you are reading in this and other issues of Peak Performance, would you be kind enough to tell others about it? Share it with your employees, friends and family. LIKE us on Facebook. Spread a good word. For legality issues: The ideas, concepts and opinions expressed in Peak Performance are, as always, intended to be used in good taste for educational purposes only. The opinions expressed or implied in these publications are not official positions of the Gazette, unless explicitly noted. Authors and publisher claim no responsibility to any person or entity for any liability, loss, or damage caused directly or indirectly as a result of the use, application or interpretation of the materials in these gazettes. Skiing is a dangerous sport. Do it at your own risk. In addition, an advertisement in Peak Performance does not constitute endorsement by Peak Performance. Main Course Language Relevant to Discussions Of the Physics of Skiing By Juris Vagners The purpose of this note is to clarify terminology and definitions related to the physics of skiing. We will review some key concepts and definitions that often enter technical discussions. 1. Inertia: This is a property of a body defined as the tendency of the body to remain in either a state of rest or in uniform (rectilinear) motion unless acted on by external, motive force. Inertia is not a force. 2. Momentum: The mass of a body times its velocity p=mv (bold denotes a vector quantity having both a magnitude and a direction of action). Again, momentum is not a force. 3. Motive forces: Forces originating outside the body capable of changing the momentum of the body, in accordance with Newton’s Second Law: The time rate of change of momentum is equal to the resultant of all external, motive forces dp/dt = F. In skiing, the motive forces capable of changing your momentum are a) 4 Peak Performance, September 2016 Page 5 gravity, b) body/ski/snow interactions, c) pole/snow interactions and d) air resistance or drag, unless you contact an outside object or get help from a friend. 4. To move your CM in any direction, you need a (net) force in that direction. And, if that force is acting on your skis, it must somehow be transmitted to the body CM. This force may be the result of what you do with your muscles, but ultimately, these movements must result in a reactive force from your environment, in the case of skiing, the snow. 5. Newton’s First Law: If F=0 then p=constant. That means if no motive forces are acting you will continue in a straight line, i.e. your velocity will be in one direction only. This means that once lateral force is removed from the skis, you move in a straight line. 6. Force: Intuitively, this is a push or a pull. 7. Center of mass (CM): A point in the body where one can place the entire mass of the body to then trace it’s movement in inertial space according to Newton’s 2nd law. A note here: when thinking about where the CM might be DO NOT forget the equipment we have on our feet in skiing. Skis, bindings, boots can contribute 25 - 30 pounds to the mass of the skier. This will move the CM of the composite of body plus equipment significantly, particularly if one starts with a small person (the effect for a 120 lb female is far greater than the effect for a 210 lb male). 8. Key observation: 1) NONE of the “inertial forces” are motive forces, i.e. cause motion, they are the result of motion and 2) Since your body sensors are fixed to your body, you DO sense them as “forces”! Specifically, this is true for centrifugal force, a much used term in skiing. Stop turning and centrifugal force disappears, turn, and it appears. So with all this information, how should we think about the physics of skiing? In my mind, the issue is simple: 1) there is nothing we can do about gravity so let it be and act the way it does, 2) unless one is a downhill racer traveling at significant speeds, we can neglect air drag, 3) the use of the pole, other than as a timing device or assistance to get to the lift, is more of a recovery move as opposed to intentional use to help change direction, thus leaving 4) the use (and misuse) of how the skis and body interact with the snow.