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# Let's get PHYSICS-cal

Physics is at the heart of many sports and recreational activities and it is puzzling that so much of the passion and advice expressed in this forum rarely gives even lip service to the fundamental forces that cause us to formulate our skiing movements.

So I begin with a thread on gravitational and centripetal force. Comments are appreciated.

The second we begin moving and put a (shaped) ski on edge we are creating an arc (circular path), and so begins dynamic changes in our body's relationship with gravitational force to deal with the onset of centripetal force.

Now someone may pull a Hillary Clinton here and say: "WHAT DIFFERENCE DOES IT MAKE!" But it does and here's why.

Gravitational force is our weight (mass*force of gravity). This force pulls us toward the center of the earth. When we are standing or sliding on our skis, this force is pulling your feet down and away from the BOTTOM of the ski. Why?  Because your mass is aligned vertically.

Centripetal force is a force which keeps a body moving with a uniform speed along a circular path (arc) and (believe it or not) pushes from the edge of the ski up the radius of the arc and through your body towards the center (furthest point from the ski along the radius).

With gravitational force, we deal with an axis which is ALLWAYS constant and vertical. From the moment we learned to walk our ability to balance has been relatively easy because we stand erect and our mass is skeletally aligned with gravity.

With centripetal force things get more complicated and precise. Upon entering a  turn, we deal with a RADIUS (but you can think of it as a tilt-able axis if you like) which is always subject to change based on the angles of your skis, velocity and mass.

In the context of centripetal force we are balancing AGAINST the skis not on them. (Aside: for all those who use the words "Weighting your ski"...STOP IT!!!)

NOW HERE'S THE NUGGET...

As a turn is enacted, your mass is no longer aligned VERTICAL to gravity. Instead, it is parsed by your body hinges and "strung out" along a non-vertical radius. We therefore we need to create angles to reach an alignment that provides optimum balance, edging and pressure throughout ALL phases of the turn. As instructors, we really need to understand these physics fundamentals because this is where the real teaching happens.

Hopefully you have notice that I have not provided any instructional or movement tips here because that was not my intent. It is simply to make some room for the physics that drive the methods for this great sport.

As a shout out, please take a look at HeluvaSkier’s frame by frame video posted here http://www.youtube.com/watch?v=RR8yG5WjkBA&list=UUixIAgNEt4KwY1YHrin7l6Q

You can see the centripetal radius in action. Depict a straight line (radius) from his outside foot up through the inside shoulder and watch how he moves, creating a “flowing” tilt of the radius from side to side. Notice how the radius (axis) becomes vertical and gravitational as he passes through the neutral zone.

Yes I am and thanks for the welcome and links to physics threads.

You're gonna LOVE @Jamt

zenny

Well come to Epic. Good topic. Yes, at the top of the turn as we get on our new edges and are so called "upside down" the building turn forces and gravity are pulling us in different directions. As we come through the fall line at apex gravity and turn forces are starting to pull on us in the same direction, downhill. This is the reason why its easy for us to tip and incline at the top of the turn and why most of our undesired skidding takes place after the fall line. You can experience this by taking a line with a weight at the end of it and swing it around your head in circles. If you swing it around horizontally flat you will have an even pull on the line. If you tilt it you will feel more pull after apex and going up and vice versa. This without getting too technical.

Why are you so particular about not using the word "weighting"? Is it because its technically wrong since weight is mass times gravity and that is constant?

JESINSTR,

Welcome! Please stay through the summer. Every aspect of skiing will be scrutinized and we will have pages of nothing but physics. I usually get a nose bleed.

Ken
Quote:
Originally Posted by tdk6

Well come to Epic. Good topic. Yes, at the top of the turn as we get on our new edges and are so called "upside down" the building turn forces and gravity are pulling us in different directions. As we come through the fall line at apex gravity and turn forces are starting to pull on us in the same direction, downhill. This is the reason why its easy for us to tip and incline at the top of the turn and why most of our undesired skidding takes place after the fall line. You can experience this by taking a line with a weight at the end of it and swing it around your head in circles. If you swing it around horizontally flat you will have an even pull on the line. If you tilt it you will feel more pull after apex and going up and vice versa. This without getting too technical.

Why are you so particular about not using the word "weighting"? Is it because its technically wrong since weight is mass times gravity and that is constant?

tdkt6 Thanks for a great contribution and bingo on the weighting verbage. Plus when communicating with students my experience is that they react to the word weight by balancing  on the ski vs against. Probably about semantics more than anything else. :-)

could someone explain how electromagnetic force is used in skiing?

Yes, semantics.... talking about weighting.... what is your take on the active vs passive weight shift concepts? In the active weight shift we lean out over our outside ski to "weight it". Put more pressure on it. Passive weight transfer would be turn forces building up pressure on the outside ski? This is something we have debated over here many times when wedging has been the topic. Basically angulation vs inside ski release.

Quote:
Originally Posted by L&AirC

JESINSTR,

Welcome! Please stay through the summer. Every aspect of skiing will be scrutinized and we will have pages of nothing but physics. I usually get a nose bleed.

Ken

Thanks Ken....you know your post script "You're either carving or you're not" would make a great thread....

Quote:
Originally Posted by JESINSTR

Thanks Ken....you know your post script "You're either carving or you're not" would make a great thread....

I believe that was two or three summers ago
Quote:
Originally Posted by tdk6

Yes, semantics.... talking about weighting.... what is your take on the active vs passive weight shift concepts? In the active weight shift we lean out over our outside ski to "weight it". Put more pressure on it. Passive weight transfer would be turn forces building up pressure on the outside ski? This is something we have debated over here many times when wedging has been the topic. Basically angulation vs inside ski release.

First of all thanks for providing the context of Wedging.   In my opinion, at the wedge and wedge turn milestones, I am first and foremost looking for success any way I can in order to get the student up the chair and down with a smile on their face.

For a wedge turn, If you advocate an active weight shift over the outside ski, I look at that as a move to flatten the ski not weight it. Combined with rotary , a flattening ski will skid and directional change of the ski will be more rapid than a ski on edge. However the move to the outside increases the angle of  the inside ski potentially blocking the progression of the turn.

If you advocate a passive weight shift carving approach, the skier is more centered and the inside does not block the turn as much. The turn takes a while to get going but when it does,  the skier is dealing with rapidly building pressures (against that sliver of an edge)  that threatens balance.

There is no right way just preferences.

In either case let me turn to what I believe is the real roadblock to success and that is we don't spend the time (starting with the straight run) to get the skier comfortable with being tall. Tall is scary!  At every milestone from straight run on up I focus on "Low to High" drills teaching upward and forward extension while on the move.  Terrain choice here is key.

Once they get comfortable in a tall position, both skis are flat enough to begin skidding with rotational movements and then I throw in the ultimate ski teaching command....PATIENCE!

So I guess if you accept my methodology for getting tall, then passive weighting is more prevalent but I will admit that, on certain frustrating occasions, you can see me doing the ole "Fill the outside bucket with water" drill.

Quote:
Originally Posted by JESINSTR

In either case let me turn to what I believe is the real roadblock to success and that is we don't spend the time (starting with the straight run) to get the skier comfortable with being tall. Tall is scary!  At every milestone from straight run on up I focus on "Low to High" drills teaching upward and forward extension while on the move.  Terrain choice here is key.

Can you describe why would you want skiers to be tall as their go-to stance? Tall strikes me as unstable when you have a platform moving underfoot - your suspension system disappears. Also, once you're "tall", you've lost the ability to build pressure underfoot through vertical movement. (Pressure momentarily increased in the act of extending, just like if you push your legs down on a scale, but then it's gone - and your only direction is down now, which relieves pressure.)

I would suggest enabling our learners to get both short and long through the joints. The difference is that long doesn't mean "up", it means "out". When we work on bend&stretch turns, for example, we're not trying to stretch "up" but rather "out". Range of motion is helpful for lots of reasons - I'm just not seeing how "tall" is an ideal starting point in a skier's stance & balance.

Quote:
Originally Posted by JESINSTR

First of all thanks for providing the context of Wedging.   In my opinion, at the wedge and wedge turn milestones, I am first and foremost looking for success any way I can in order to get the student up the chair and down with a smile on their face.

For a wedge turn, If you advocate an active weight shift over the outside ski, I look at that as a move to flatten the ski not weight it. Combined with rotary , a flattening ski will skid and directional change of the ski will be more rapid than a ski on edge. However the move to the outside increases the angle of  the inside ski potentially blocking the progression of the turn.

If you advocate a passive weight shift carving approach, the skier is more centered and the inside does not block the turn as much. The turn takes a while to get going but when it does,  the skier is dealing with rapidly building pressures (against that sliver of an edge)  that threatens balance.

There is no right way just preferences.

In either case let me turn to what I believe is the real roadblock to success and that is we don't spend the time (starting with the straight run) to get the skier comfortable with being tall. Tall is scary!  At every milestone from straight run on up I focus on "Low to High" drills teaching upward and forward extension while on the move.  Terrain choice here is key.

Once they get comfortable in a tall position, both skis are flat enough to begin skidding with rotational movements and then I throw in the ultimate ski teaching command....PATIENCE!

So I guess if you accept my methodology for getting tall, then passive weighting is more prevalent but I will admit that, on certain frustrating occasions, you can see me doing the ole "Fill the outside bucket with water" drill.

Wow TDK6 and jesinstr, perhaps it's time to resurrect the passive vs. active weight shift thread???..

Jeninstr, do you find that your students have difficulty discovering parallel turning mechanics?

Quote:
Originally Posted by JESINSTR

For a wedge turn, If you advocate an active weight shift over the outside ski, I look at that as a move to flatten the ski not weight it. Combined with rotary , a flattening ski will skid and directional change of the ski will be more rapid than a ski on edge. However the move to the outside increases the angle of  the inside ski potentially blocking the progression of the turn.

If you advocate a passive weight shift carving approach, the skier is more centered and the inside does not block the turn as much. The turn takes a while to get going but when it does,  the skier is dealing with rapidly building pressures (against that sliver of an edge)  that threatens balance.

There is no right way just preferences.

In either case let me turn to what I believe is the real roadblock to success and that is we don't spend the time (starting with the straight run) to get the skier comfortable with being tall. Tall is scary!  At every milestone from straight run on up I focus on "Low to High" drills teaching upward and forward extension while on the move.  Terrain choice here is key.

Once they get comfortable in a tall position, both skis are flat enough to begin skidding with rotational movements and then I throw in the ultimate ski teaching command....PATIENCE!

So I guess if you accept my methodology for getting tall, then passive weighting is more prevalent but I will admit that, on certain frustrating occasions, you can see me doing the ole "Fill the outside bucket with water" drill.

"For a wedge turn, If you advocate an active weight shift over the outside ski, I look at that as a move to flatten the ski not weight it. Combined with rotary , a flattening ski will skid and directional change of the ski will be more rapid than a ski on edge. However the move to the outside increases the angle of  the inside ski potentially blocking the progression of the turn."

So you want to move out over the outside ski to "flatten" it not weight it so you can twist it easier, this in turn will make the ski change direction quicker?  Hmmmm?

and this move does admittedly increases the angle of the inside ski which blocks the progression of the turn?

That sounds a bit antagonistic to me?….  Why would I want to do that?

"If you advocate a passive weight shift carving approach, the skier is more centered and the inside does not block the turn as much. The turn takes a while to get going but when it does,  the skier is dealing with rapidly building pressures (against that sliver of an edge)  that threatens balance."

I never knew a passive weight shift in a wedge turn produced a carve?  Balancing on a sliver of an edge threatens balance?  What do you think may happen if we keep the outside ski flatter in the passive weight shift wedge turn so it can be steered and use the positive attributes of being more centered and keeping the inside ski at a low edge angle so it can be steered too?  What could possibly happen here?

Welcome to Epicski JESINSTR, I think you will enjoy it here and learn a great deal and become a better instructor!  Dig in, grab a drink and hang on!

Thanks Jenister for your postings and Bud for joining in. I wasn't so much interested in getting into a preference debate, rather technically define active and passive weight shift. From a technical standpoint. Is this terminology completely false? That would not mean that we should stop using it, just to be aware of what is correct and what is not. In case the collage physics professor ends up as our student one sunny day.

Jenister, here are my definitions of active and passive weight transfer in the context of wedging. Bud correct me if I'm wrong. Starting point for both is a wedge stance with both BigToeEdges engaged and sliding over the snow at slow or medium speed

Active weight transfer: keep edge angles unaltered on both skis, bend your upper body sideways at hips/waist to shift your CoM out over your new outside ski (note, you don't flatten the new outside ski)

Passive weight transfer: flatten you new inside skis edge angle and feel the pressure increase on your new outside ski with unaltered edge angle.

Note that an active weight transfer can be performed at a standstill while a passive cant.

I have not followed the active vs passive debate in detail, but what about both? -Tip/untip AND lighten the inside ski.

Jamt, yes, sort of.

Quote:
Originally Posted by tdk6

Note that an active weight transfer can be performed at a standstill while a passive cant.

And this has what to do with skiing. If I'm not moving then I'm not skiing. One of your sillier statements.

fom

You gotta get moving somehow, don't you, FOM?

JesInstr--welcome to EpicSki. As others have suggested, you have an incredible archive of skiing discussions, some good, some not so, in front of you. You could sit back and spend all summer just catching up!

I am with the others in wondering why you would want to initiate a turn--wedge or otherwise--by moving in the wrong direction (up the hill and away from the intended turn direction) and flattening your outside ski. Shouldn't you move into the turn while tipping the ski(s) to their new edges?

Best regards,

Bob Barnes

Quote:
Originally Posted by Metaphor_

Can you describe why would you want skiers to be tall as their go-to stance? Tall strikes me as unstable when you have a platform moving underfoot - your suspension system disappears. Also, once you're "tall", you've lost the ability to build pressure underfoot through vertical movement. (Pressure momentarily increased in the act of extending, just like if you push your legs down on a scale, but then it's gone - and your only direction is down now, which relieves pressure.)

I would suggest enabling our learners to get both short and long through the joints. The difference is that long doesn't mean "up", it means "out". When we work on bend&stretch turns, for example, we're not trying to stretch "up" but rather "out". Range of motion is helpful for lots of reasons - I'm just not seeing how "tall" is an ideal starting point in a skier's stance & balan

Valid questions and good points Metaphor and they take me to my philosophy of teaching which unfortunately is way off the purpose of this thread but this is important so here goes.  First and foremost, I focus on developing skills (dynamic balance, rotation, edging and pressure) almost exclusively in the entry levels of skiing. Critical to skill development (my opinion) is that you address the entire spectrum of the skill. Take dynamic balance for instance. I do all kinds of exercises to widen the range of balance. It makes applying technique that much easier. You are right, tall is unstable but that doesn't mean you ignore going there and tall (extended) and forward (at the beginner/straight run level) is within the dynamic balance spectrum.  It may take a little more time to develop the spectrum but in the end it allows the student to find the center more easily and definitively.  So these are skill development exercises and nothing more.

There has been this age old argument in our profession about the wisdom of teaching one thing and then having to "un-teach" it.  I have come to the conclusion that if your objective is to provide a rewarding skiing experience to the entry level skier so that there is an outside chance they will return next week, we have no alternative.  The conflict between self preservation and ski efficiency is too great at this level (and probably most all levels).  Using a skills focused approach says it is not about un-teaching but really about change. If your skill set is developed, change is easy, if not, it is hard.   I would like to think that my skill set is developed enough so that if the director of the Church of Powder Day Saints came out and said "we are now go to teach customers to ski on their head" I could figure a way to do that.

The point I am taking away from this exchange is that I need to be more articulate and contextual in my posts in terms of skills vs technique.

Quote:
Originally Posted by bud heishman

Wow TDK6 and jesinstr, perhaps it's time to resurrect the passive vs. active weight shift thread???..

Jeninstr, do you find that your students have difficulty discovering parallel turning mechanics?

Bud, Please accept my apologies and ref my response to Metaphor.  I didn't want to go down the active/passive rabbit hole

(which is not one of my strong points.) I know...I need to be more careful.

Well it is not a rabbit hole, rather an area the begs for better understanding on your part which will possibly create one of many epiphanies to come in your skiing and teaching career.

Quote:
Originally Posted by Bob Barnes

You gotta get moving somehow, don't you, FOM?

JesInstr--welcome to EpicSki. As others have suggested, you have an incredible archive of skiing discussions, some good, some not so, in front of you. You could sit back and spend all summer just catching up!

I am with the others in wondering why you would want to initiate a turn--wedge or otherwise--by moving in the wrong direction (up the hill and away from the intended turn direction) and flattening your outside ski. Shouldn't you move into the turn while tipping the ski(s) to their new edges?

Best regards,

Bob Barnes

Bob, (and others) Please see my response to Metaphor.  I made a forum rookie mistake regarding my intent. sorry.

Quote:
Originally Posted by bud heishman

Well it is not a rabbit hole, rather an area the begs for better understanding on your part which will possibly create one of many epiphanies to come in your skiing and teaching career.

Understand.

No worries amigo!  Again, welcome, settle in and keep an open mind.  Epicski instructional forum is a fun place to share knowledge and questions with other passionate skiers and professionals.  Careful not to make statements as fact unless you can back them up or the gang will call you out.  You will find there are some very knowledgeable instructors and coaches who frequent this forum from around the world and we have some heated discussions from time to time.  Keep your cool and dive in!

Quote:
Originally Posted by JESINSTR

There has been this age old argument in our profession about the wisdom of teaching one thing and then having to "un-teach" it.  I have come to the conclusion that if your objective is to provide a rewarding skiing experience to the entry level skier so that there is an outside chance they will return next week, we have no alternative.  The conflict between self preservation and ski efficiency is too great at this level (and probably most all levels).  Using a skills focused approach says it is not about un-teaching but really about change. If your skill set is developed, change is easy, if not, it is hard.   I would like to think that my skill set is developed enough so that if the director of the Church of Powder Day Saints came out and said "we are now go to teach customers to ski on their head" I could figure a way to do that.

The point I am taking away from this exchange is that I need to be more articulate and contextual in my posts in terms of skills vs technique.

I don't think there is a debate at all. A wide spread fundamental misunderstanding about what is taught and why, yes.
A positive experience can be provided with clear and realistic goal setting. A lesson plan that provides multiple small and encouraging successful outcomes on appropriate terrain. It looks to the future and creates new goals and challenges that require incremental skill development and no relearnibg.
A frustrating lesson is the failure of an instructor to assess and make appropriate goal setting and terrain selection.
Re - learning would only serve to weaken trust and the learning partnership.
Quote:
Originally Posted by fatoldman

And this has what to do with skiing. If I'm not moving then I'm not skiing. One of your sillier statements.

fom

No offence taken fatoldman.... think..... weight = mass x g..... see, its not speed dependent.

Quote:
Originally Posted by tdk6

Note that an active weight transfer can be performed at a standstill while a passive cant.

Quote:
Originally Posted by fatoldman

And this has what to do with skiing. If I'm not moving then I'm not skiing. One of your sillier statements.

fom

Quote:
Originally Posted by Bob Barnes

You gotta get moving somehow, don't you, FOM?

Bob,

This brings up a couple interesting questions. If you are at a standstill in a wedge stance will a weight shift by itself produce movement? Will the act of flattening one of the skis (releasing) by itself produce movement? Assume you are on a slope not a flat for this.

I think the answers to these questions will say a lot about why I teach what I do in this 'go' sport of skiing.

fom

Sorry, not Bob here but I think we both know the answer to your query

Assuming we are standing stationary across the fall line in a wedge, an active weight transfer will not in and of itself produce movement or a turn initiation.  To the contrary, beginning from the same position, by releasing the edge grip of the down hill ski will produce forward movement, tips to seek the fall line and consequently cause a more passive weight shift to the outside ski and a turn.   One is a Don't go movement and the other is a "GO" movement.

TDK6 is still stuck in the 60's

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