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# Two kinds of Wedge Christie - Page 26

Quote:
Originally Posted by borntoski683

Actually on another look, Daneen is using a push off also but his is much smoother then Aiko's.

He twists it while its in the air and he's anchored on the other foot, and sets it down with steering angle, then brush carves it out.

Below are still shots from the Deneen video around 1:49 progressing in time.  The change in angle of his legs shows that his body is moving towards the old outside ski.  This means that he can not be pushing off the old outside ski, because you move away from something you are pushing off of.  Saying that he his pushing off the old outside ski is like saying when a baseball pitcher releases the pitch aimed at the batter the ball will go to the outfield.  He is moving away from his new outside ski before putting weight on it, so he has no lateral momentum moving towards the outside ski to push against.  Therefore, the snow cannot convert momentum into rotation where the tails displace more than the tips.  (Fulcrum has to switch sides when the momentum switches to get the same spin direction)

Also, in picture 2 and 3, his skis are facing approximately straight ahead.  In frame two, his new outside ski tip is on the ground, but not under the boot.  Then in frame 3, under the boot is now on the ground too, showing that he has put weight on the ski before it has rotated.  Frame 4 shows the rotation beginning shortly after lifting the inside ski.

When the skis have rotated past the fall line, gravity aids in washing out the tails.  When the skis haven't yet rotated past the fall line, gravity opposes the tails washing out.  Gravity cannot wash his tails out because he has not rotated past the fall line.  At the transition from one turn to the next there is no centrifugal force, so the only forces available to rotate the ski beyond the skis' turning radius must come from the leg.

Edited by The Engineer - 11/23/15 at 7:13am

How do you get gravity to act just on the tail of the ski instead of the whole ski. This is a major breakthrough in the field of physics.

fom

Quote:
Originally Posted by fatoldman

How do you get gravity to act just on the tail of the ski instead of the whole ski. This is a major breakthrough in the field of physics.

fom

Having more friction on the front of the ski than the back of the ski creates a fulcrum to spin around like a pendulum.  The tail is like the ball in this pendulum analogy.  When the skis are past the fall line it's like the pendulum rotating down to the bottom pulled by gravity.  When the skis are rotated before the fall line it's like the pendulum swinging up and being slowed by gravity.  It's so funny to hear such sarcasm when the answer is so simple.  Why don't you ask BTS how do you get lateral momentum to rotate the ski with such stupid sarcasm?  We've been discussing linear forces rotating the ski around the fulcrum.  It's the only possible way any of BTS's arguments make any sense at all.  If your tails are more detuned than the tips they can lose grip first.  More pressure on the front of the ski can give better edge grip on the front, you can have a variable surface with more friction in one part of the ski than another.....  You're hilarious fatoldman, such wit with that fancy sarcasm, if only it wasn't so easy to get gravity to move the tails more than the tips you would have really got me.

Edited by The Engineer - 11/23/15 at 11:04am

You seem to think that gravity is pulling the skis tails down the hill, I thought that gravity only acted to accelerate objects toward the center of the earth.

1. Gravity pulls towards the centre of the earth, not down the fall line.  Unless the slope is 90 degrees, gravity can so assist in washing out the heels before the fall line.

2. He is pushing his heels a bit, the timing of the push is key.

As I said...Daneen is way more refined then Aiko.  Aiko was doing a very blatant push away move.  Daneen is generally doing a much more refined weight transfer.  However, its essentially the same thing in terms of using the downhill ski as an anchor to move to the other ski..in his case he sometimes sets the ski down without rotary and brush carves it very smoothly, in other cases he rotates it in the air (opposite of YM's question) and sets it down with some steering angle.  Sometimes when he sets it down rotated, it washes out some more.    Its basically the same thing, his is just much quieter and more refined and doesn't have a blatant push away that Aiko's has.

Quote:
Originally Posted by fatoldman

You seem to think that gravity is pulling the skis tails down the hill, I thought that gravity only acted to accelerate objects toward the center of the earth.

Gravity pulls to the center of the earth, but it's a vector, which means there is still a force in other directions, but it's just less.  The force of gravity pointing down the slope is reduced by the angle of the slope according to a cos or sin function.  If straight down is angle 0 degrees then cos(0) is 1 and you get full gravity force pulling you.  If the angle is 60 degrees then the force pointing along the slope is cos (60) which is half the force.  A flat slope would be angle 90 degrees in this frame of reference and cos(90) is 0, so there is no force to push the tails around a fulcrum from gravity on a flat slope.  So, if there's any angle to the slope, gravity can spin those skis around a fulcrum.  Basically, you have to consider the net force.  If there is another force in the system that opposes gravity but the direction of maximum force is pointing at a different angle, then the vectors will now add to have a net force with a maximum intensity pointing in a new direction.  In other words, when adding vectors you have to combine magnitude and angle to get the resultant magnitude and angle.  With electromagnetic fields you can repeatedly filter out portions of the electric field vector pointing in a different direction and rotate the polarity to point a way it originally had zero magnitude.  Now that's wild. So, this proportionality in different directions is real.

There is also existing momentum, not just gravity.

This is a bit of a tangent, but here's a hypothetical question for you TE.  Two skiers are skiing next to each other going straight down, on the same slope, they have exactly the same tuned skis, weigh exactly the same, and all factors are equal.  Thusly they are going exactly the same speed and are in an even tie in their little race.

One of them gets air off a bump, and is airborne for 10 feet but only one inch off the snow.  While in the air, who is going faster?  Upon landing, who is further ahead?  And why.

Quote:
Originally Posted by The Engineer

Quote:
Originally Posted by fatoldman

You seem to think that gravity is pulling the skis tails down the hill, I thought that gravity only acted to accelerate objects toward the center of the earth.

Gravity pulls to the center of the earth, but it's a vector, which means there is still a force in other directions, but it's just less.  The force of gravity pointing down the slope is reduced by the angle of the slope according to a cos or sin function.  If straight down is angle 0 degrees then cos(0) is 1 and you get full gravity force pulling you.  If the angle is 60 degrees then the force pointing along the slope is cos (60) which is half the force.  A flat slope would be angle 90 degrees in this frame of reference and cos(90) is 0, so there is no force to push the tails around a fulcrum from gravity on a flat slope.  So, if there's any angle to the slope, gravity can spin those skis around a fulcrum.  Basically, you have to consider the net force.  If there is another force in the system that opposes gravity but the direction of maximum force is pointing at a different angle, then the vectors will now add to have a net force with a maximum intensity pointing in a new direction.  In other words, when adding vectors you have to combine magnitude and angle to get the resultant magnitude and angle.  With electromagnetic fields you can repeatedly filter out portions of the electric field vector pointing in a different direction and rotate the polarity to point a way it originally had zero magnitude.  Now that's wild. So, this proportionality in different directions is real.

You seem to have forgotten the broomstick example.  Legs at an weight applied assists heel wash, further assisted by heel push.

P.S. he is indeed pushing his lower body back and forth.

Quote:
Originally Posted by Ghost

You seem to have forgotten the broomstick example.  Legs at an weight applied assists heel wash, further assisted by heel push.

P.S. he is indeed pushing his lower body back and forth.

I didn't forget it.  I explained it already.  The broom example requires a triangle shape.  With the feet together, you can't push off of one ski against the other without the feet coming apart.  And when you do, you'll see the body moving away from the ski that you are pushing off of.  It's impossible in the Deneen video for him to push off of the ski that he is getting closer to create momentum to push his other ski out.  Remember that the old outside ski is in the air when the new ski starts rotating.  He can't push anymore when the ski is in the air.  It can only be from momentum and the momentum is clearly shown to be going the opposite direction.

Quote:
Originally Posted by borntoski683

There is also existing momentum, not just gravity.

This is a bit of a tangent, but here's a hypothetical question for you TE.  Two skiers are skiing next to each other going straight down, on the same slope, they have exactly the same tuned skis, weigh exactly the same, and all factors are equal.  Thusly they are going exactly the same speed and are in an even tie in their little race.

One of them gets air off a bump, and is airborne for 10 feet but only one inch off the snow.  While in the air, who is going faster?  Upon landing, who is further ahead?  And why.

Here's a hint... does ground Reaction force contribute to velocity?

Quote:
Originally Posted by borntoski683

There is also existing momentum, not just gravity.

This is a bit of a tangent, but here's a hypothetical question for you TE.  Two skiers are skiing next to each other going straight down, on the same slope, they have exactly the same tuned skis, weigh exactly the same, and all factors are equal.  Thusly they are going exactly the same speed and are in an even tie in their little race.

One of them gets air off a bump, and is airborne for 10 feet but only one inch off the snow.  While in the air, who is going faster?  Upon landing, who is further ahead?  And why.

The guy going off the jump has to first experience less acceleration from gravity, so the guy not going off the jump will be faster and farther ahead as a function of time.

Quote:
Originally Posted by The Engineer

I didn't forget it.  I explained it already.  The broom example requires a triangle shape.  With the feet together, you can't push off of one ski against the other without the feet coming apart.  And when you do, you'll see the body moving away from the ski that you are pushing off of.  It's impossible in the Deneen video for him to push off of the ski that he is getting closer to create momentum to push his other ski out.  Remember that the old outside ski is in the air when the new ski starts rotating.  He can't push anymore when the ski is in the air.  It can only be from momentum and the momentum is clearly shown to be going the opposite direction.

TE, clearly they are talking about what he does after setting the uphill/outside ski down.  You're talking in circles now.

Can it be pushed once he has transferred weight to it?  Does the leg have any RoM to actually push it away?  Personally I don't think he is doing that appreciably, but I should watch the video again, but its certainly possible, if the ski is set down with some steering angle and if the skier applies some extension movement in the leg...the ski can be pushed into a washed out skid away from the body...

Quote:
Originally Posted by The Engineer

The guy going off the jump has to first experience less acceleration from gravity, so the guy not going off the jump will be faster and farther ahead as a function of time.

Quote:
Originally Posted by borntoski683

Here's a hint... does ground Reaction force contribute to velocity?

Ground reaction force is the force vector that combines with the gravity force to determine net acceleration.  So, when I say he will accelerate less that's why of course.

Here's a question for you now BTS.  If you are pushing off a ski how does the angle your legs make with the ground change while you are pushing?  Once you can understand that along with Ghost, then you will understand how it's impossible for Deneen to be pushing off as shown in the still frame progression.  I don't believe that you have any motivation to understand it, and you're just doing argumentative banter, so I leave you with the option to learn something or not.  Energy is 1/2mv^2.  Momentum is mv.  Energy and momentum are linked through velocity.  Energy is force times distance, so you have to push through a distance to get velocity.  Pushing through a distance with a finite force takes time.  The greater the momentum the more the tails could wash out in your ridiculous snow rotation theory the longer someone has to push off, so to generate enough momentum you have to see the skier moving away from the thing he is pushing off of not toward, and the angles the legs make with the ground show the direction of movement.  Which way is which?  I'll let you work on that.  I'm out, but if you ever feel like really learning this stuff instead of just internet, ego battling, we could have a real discussion.

Again TE...read more carefully.... you are talking about 3 or 5 or 6 different things at once and conflating them all as it would amuse you it would seem..

round and round in circles we go...where it stops nobody knows...

The "push off" was related to Aiko and her downhill ski, not daneen.  Daneen is doing a weight transfer from the downhill ski to the uphill ski...but I would not label it a "push off".  I have tried to make that clear, you seem to be ignoring that now..

Once he transfers weight to that new ski, do you think its possible for him to push his new outside ski away from himself?  you say its not possible.  I say otherwise.

Momentum, including angular momentum is like a bank, deposits and withdrawals can be made a different points in time.  It can also be transferred between accounts (moved around to different body parts) at different times.  Just say'n.

Quote:
Originally Posted by The Engineer

Gravity pulls to the center of the earth, but it's a vector, which means there is still a force in other directions, but it's just less.  The force of gravity pointing down the slope is reduced by the angle of the slope according to a cos or sin function.  If straight down is angle 0 degrees then cos(0) is 1 and you get full gravity force pulling you.  If the angle is 60 degrees then the force pointing along the slope is cos (60) which is half the force.  A flat slope would be angle 90 degrees in this frame of reference and cos(90) is 0, so there is no force to push the tails around a fulcrum from gravity on a flat slope.  So, if there's any angle to the slope, gravity can spin those skis around a fulcrum.  Basically, you have to consider the net force.  If there is another force in the system that opposes gravity but the direction of maximum force is pointing at a different angle, then the vectors will now add to have a net force with a maximum intensity pointing in a new direction.  In other words, when adding vectors you have to combine magnitude and angle to get the resultant magnitude and angle.  With electromagnetic fields you can repeatedly filter out portions of the electric field vector pointing in a different direction and rotate the polarity to point a way it originally had zero magnitude.  Now that's wild. So, this proportionality in different directions is real.

Fortunately what you say is true. Were it not we couldn't ski at all and that would be sad.
Quote:
Originally Posted by JESINSTR

Jack,

Product marketing videos made in the name of skiing improvement are often misleading and inaccurate and this one is no exception.

The purpose of the Javelin turn is not to "square you up down the hill".  That result only happens when you execute Javelin turns in a short radius pattern as he tries (and sometimes fails) to do in the video.

The true purpose is develop alignment against the outside ski to create and perpetuate a circular path for which the modern edged ski is designed to do. Hip alignment is relational to the ski so as to effect ski shape and deal with pressure from the resultant centripetal force.  In his demos, you see numerous times that Deneen's hips leave square. That's not because he is doing it wrong, it is because his radius has increased in size for that particular turn.

Now on to the line item "tips"....ie  when they freeze the frame and insert text....

- His weight is not on the outside ski.  His mass is aligned and balanced against the outside ski.  What if all motion stopped while in that position?  Would he remain standing?

Not symantics.  It is important that skiers understand the difference between gravitational speak  ("weight" and "on") vs centripetal speak ("mass" and "against").  That difference is what the Javelin Turn is all about.

- Next,  "Lower Body position keeps weight forward...." I would submit that his inside lower body position (normally with both feet on the snow) is a result of a shortening of the inside leg which is the way we create a higher edge and derive more turning power from the outside ski. Obviously in the Javelin turn the inside ski is in the air...but the leg is shorter!!

- Hips Square to the hill.... Correct if you are trying to maintain directional travel straight down the  hill but as I stated above many of his demo turns belie that statement.

- Separation-  Finally something straight forward and accurate!

- Shoulder stacked over the hips... That's 2 right....we're on a roll!

- Eyes up and Forward.   OH NO!!! That would be number 3 except for that fact that is not what he says!!! He says to keep the eyes looking down hill!   Boy, the Hart producers sure missed that one!

For someone of champion status to say in a video to keep your eyes facing down hill without expressly invoking context does more harm than anything to the wannabie skier that wants to improve.   I know that in his world it is all about going down hill, but in most all sports we go where our eyes lead us and since the Javelin turn takes us in a circle the eyes need to coordinate and encourage that travel until one decides to release and go the other way.

Finally contrary to what Deneen implied,  you really don't need the Hart F17 world cup ski to be a good skier...kind of a cheezy product plug in my opinion.

Cheezy marketing production makes this industry and other industries go around and around.........

Here's Deneen with Dynastar Twister, imo a very good mogul ski. I will dread the day Dynastar discontinue this product. IIRC, I saw a vid clip of him on twister doing javelins as well   :!

Quote:
Originally Posted by borntoski683

Once he transfers weight to that new ski, do you think its possible for him to push his new outside ski away from himself?  you say its not possible.  I say otherwise.

BTS, there may have been some confusion about which ski we’re discussing, the old outside ski or the new outside ski.  So, this leaves more that hasn’t been discussed, and I should respond.  I thought you’ve been referring to the old outside ski, because I considered that you were aware of the balance issues with pushing off the new outside ski.  Up to this point, I’ve been considering all the ways that the ski can rotate while staying balanced. You can push out the outside ski that you are standing on and if the front has more grip than the back, the ski will rotate, but when it’s your only leverage point and you have no lateral momentum or force toward that ski, you will fall over.  The only way to keep from falling over is if the ski curves around fast enough to allow centrifugal forces to build to catch you.  A carved turn may be predictable enough to rely on the ski turning itself, but not a rotary turn.  If he tries to push out that outside ski and the tail catches on a clump of crud, the ski will not rotate predictably and it will not be able to come around to catch him and he will fall over.  Or let’s say it’s very icy and he just loses grip everywhere on the ski when pushing it out, it won’t rotate and he will fall.  If you are balanced you can deal with this surface variation by making adjustments.  Leg rotary allows the ski to rotate faster than the turning radius of the ski while maintaining balance.

Perhaps your questions about reactionary force are demonstrating the thing you are missing with this.  The reactionary force on the ground is not what is accelerating the skier down the slope.  It’s all about energy.  All the energy is coming from the gravitational field.  The reactionary force is perpendicular to the direction of travel.  The reactionary force does not contribute a single drop of energy to accelerate the person down the slope.  All the reactionary force does is cancel gravitational force pointing perpendicular to the ground, so that only the component of gravity pointing down the slope remains.  Gravity is the only thing pulling you down the slope.  The snow can not provide a reactionary force to rotate the ski all by itself.  All it does is prevent movement on one end, and it’s energy from another force that provides the energy to rotate.  Where does that energy come from?  Here are some possibilities.

1.  Gravity.  Nope, above fall line.

2.  Centrifugal force.  Nope, none at turn transition.

3.  Inertia from lateral momentum from pushing off the old outside ski.  Nope, video shows momentum going the opposite direction.

4.  Forward momentum converted to lateral momentum by placing the ski at an angle.  Nope, still shot progression shows weight on ski going straight not being placed at an angle.

5.  Lateral force exerted by leg.  Nope, can’t maintain balance.

6.  Rotary force from rolling the knee.  Yup, we see the knee roll.  Many mogul skiers know to roll the knee to rotate the ski and do it on purpose.  Rolling the knee provides the right pressure and rotational force to reliably rotate the ski faster than the turning radius to stay balanced.

TE there are a few ways to stay in balance when a ski washes out and the fact that the tail washes out is one of them. You can also counter balance. When a ski carves into balanced orientation as you described, the same thing happens when the tail washes out, only faster!

I was not actually the one that suggested tail pushing is happening. Others did. I don't particularly think he is pushing the tails. I was just responding to your comment that you didn't think it was possible. Now that you understand what was being suggested perhaps we're on the same page?

But I don't actually think these skiers were pushing their tails away. I have described already what I think they are doing, read it again if you are interested.
Quote:
Originally Posted by The Engineer

6.  Rotary force from rolling the knee.  Yup, we see the knee roll.  Many mogul skiers know to roll the knee to rotate the ski and do it on purpose.  Rolling the knee provides the right pressure and rotational force to reliably rotate the ski faster than the turning radius to stay balanced.

Please explain in more detail how rolling the knee rotates the ski.  Feel free to use forces, torques, axis of rotation, rotational inertia, and any other engineering terms you wish. Thanks.

Quote:
Originally Posted by borntoski683

TE there are a few ways to stay in balance when a ski washes out and the fact that the tail washes out is one of them. You can also counter balance. When a ski carves into balanced orientation as you described, the same thing happens when the tail washes out, only faster!

Excellent point.  You can counter balance and it is part of it, but not enough without controlled leg rotation.

Some more responses...

Quote:

Originally Posted by The Engineer

You can push out the outside ski that you are standing on and if the front has more grip than the back, the ski will rotate, but when it’s your only leverage point and you have no lateral momentum or force toward that ski, you will fall over.  The only way to keep from falling over is if the ski curves around fast enough to allow centrifugal forces to build to catch you.  A carved turn may be predictable enough to rely on the ski turning itself, but not a rotary turn.

Well if the skier is moving, then there is some momentum, not "none".  But here is the thing.  When the ski carves or rotates into steering angle, lateral force is created...  In fact for rotary turns this is created even faster then carved turns.

Quote:
Originally Posted by The Engineer

The only way to keep from falling over is if the ski curves around fast enough to allow centrifugal forces to build to catch you.  A carved turn may be predictable enough to rely on the ski turning itself, but not a rotary turn.

You simply need centripetal reactionary forces created lateral to the direction the skis are pointing.  Your momentum is converted into those lateral forces when you edge the ski with steering angle.  rotating the ski accelerates the process of obtaining steering angle and lateral forces actually.  Carving the ski may get there also and there are huge benefits to carving, but the balance requirements for carving are actually higher then rotating, not the other way around.  Rotating is a way to compensate for poor balance in fact.

Quote:
Originally Posted by The Engineer

Or let’s say it’s very icy and he just loses grip everywhere on the ski when pushing it out, it won’t rotate and he will fall.  If you are balanced you can deal with this surface variation by making adjustments.

I agree tail pushing is generally bad.  I personally don't think either of them were pushing their tails.  I was only responding to your previous claim that it wasn't possible to push the tails.

Quote:
Originally Posted by The Engineer

Perhaps your questions about reactionary force are demonstrating the thing you are missing with this.  The reactionary force on the ground is not what is accelerating the skier down the slope.  It’s all about energy.  All the energy is coming from the gravitational field.  The reactionary force is perpendicular to the direction of travel.  The reactionary force does not contribute a single drop of energy to accelerate the person down the slope.  All the reactionary force does is cancel gravitational force pointing perpendicular to the ground, so that only the component of gravity pointing down the slope remains.  Gravity is the only thing pulling you down the slope.  The snow can not provide a reactionary force to rotate the ski all by itself.  All it does is prevent movement on one end, and it’s energy from another force that provides the energy to rotate.  Where does that energy come from?  Here are some possibilities.

What is it you think I am missing exactly TE?  Nobody has said anything about energy thus far.  Acceleration is caused by external forces.  Gravity is one external force, but the snow reaction force is also another external force that does accelerate the skier into new directions.  As Ghost said earlier, momentum is like a bank account.  When you engage your skis and obtain reactionary forces, that stored energy is converted..and this can definitely result in acceleration in new directions, including up a hill, away from gravity, up into the air, down the hill, across the hill, high siding out of the turn and many other ways...all of that is facilitated by the ski snow reactionary forces that are created by harnessing the momentum.  Even at very slow speeds, there is momentum which can be harnessed through the ski snow reaction.  If that were not the case, a wedging skier would not make any turn at all, as turning is in fact acceleration in a new direction, and that new direction could be completely away from gravity even!  The snow can definitely cause the skier to turn and can definitely cause the ski to rotate.

this is the same old tired discussion found many times on this site...Its hard to believe you are really an engineer.

Quote:
Originally Posted by Ghost

Please explain in more detail how rolling the knee rotates the ski.  Feel free to use forces, torques, axis of rotation, rotational inertia, and any other engineering terms you wish. Thanks.

Knee bone connected to the thigh bone

Thigh bone connected to the hip bone

Hip bone connected to the back bone

Rotate the femur and you rotate the ski.  But, as I said before, it rotates in a way that applies more pressure to the front of the ski which helps to pivot around a fulcrum.  You know I do have things to do Ghost, and proving things beyond a reasonable doubt is not one of them.

Quote:
Originally Posted by The Engineer

Excellent point.  You can counter balance and it is part of it, but not enough without controlled leg rotation.

without the ski pivoting...

whether or not the leg twisted the ski with rotary force is still the question..

and I still say you can't stand on a single ski and twist it without either blatant counter rotation or some other stabilizing point of the body.

Quote:
Originally Posted by The Engineer

Quote:
Originally Posted by Ghost

Please explain in more detail how rolling the knee rotates the ski.  Feel free to use forces, torques, axis of rotation, rotational inertia, and any other engineering terms you wish. Thanks.

Knee bone connected to the thigh bone

Thigh bone connected to the hip bone

Hip bone connected to the back bone

Rotate the femur and you rotate the ski.  But, as I said before, it rotates in a way that applies more pressure to the front of the ski which helps to pivot around a fulcrum.  You know I do have things to do Ghost, and proving things beyond a reasonable doubt is not one of them.

It's not quite that simple. For example, ff your femur is horizontal, rotating it will tip the ski, and the tipped ski moving forward will interact with the snow.   It is the external reaction force at the tip of the ski that is rotating the ski.  If your femur is vertical, rotating it rotates the ski directly and inefficiently.

Quote:
Originally Posted by borntoski683

Well if the skier is moving, then there is some momentum, not "none".  But here is the thing.  When the ski carves or rotates into steering angle, lateral force is created...  In fact for rotary turns this is created even faster then carved turns.

I discussed this, lateral momentum vs forward momentum.  It's a vector thing.

You simply need centripetal reactionary forces created lateral to the direction the skis are pointing.  Your momentum is converted into those lateral forces when you edge the ski with steering angle.  rotating the ski accelerates the process of obtaining steering angle and lateral forces actually.  Carving the ski may get there also and there are huge benefits to carving, but the balance requirements for carving are actually higher then rotating, not the other way around.  Rotating is a way to compensate for poor balance in fact.

Later in the turn, not at the beginning where he is first rotating.

What is it you think I am missing exactly TE?  Nobody has said anything about energy thus far.  Acceleration is caused by external forces.  Gravity is one external force, but the snow reaction force is also another external force that does accelerate the skier into new directions.  As Ghost said earlier, momentum is like a bank account.

Momentum is a bank account, but because it's based on velocity you can see how much you saved up by seeing which direction they are moving.  If they are not moving in a particular direction there is no momentum in that direction.

this is the same old tired discussion found many times on this site...Its hard to believe you are really an engineer.

What a pile of crap.  The last time someone tried to pull that move, was Bob when he thought I made a mistake regarding nonlinear snow friction.  But, he was completely wrong, fluid type drag from snow is well understood, so you might want to check the facts before jumping on that bandwagon.  I graduated top 10% from a prestigious engineering school.  Received my Ph.D. off a very successful innovative idea.  Have been a main technical driver for our company over the last 15 years.  I've personally developed innovative products that we sell all over the world to places such as Jet Propulsion Lab, Max Plank, DARPA.  I've worked with scientists from institutions such as these to provide technical solutions to solve their problems.  My methods work.  I solve problems, and I have the track record to prove it.  There's one extremely idiotic thing I've done, and that's to try to have a technical conversation with someone who is completely rigid in their viewpoint.  The truth is that if it's just you and me, I wouldn't even bother.  The only reason I've continued this discussion is because Ghost was weighing in, and he has enough technical knowledge and background to contribute, though he's kind of been asleep at the wheel.  I believe it's impossible to convince you no matter what the facts, but I thought I could convince Ghost.  But, now I believe you are both so entrenched it's not going anywhere.  I've noticed an open window for Ghost at times where it can be a give and take conversation, but I've seen that window shut too.  What really blows my mind is that I easily could have one of the strongest technical resumes in this forum directly relating to these physics discussion, and I've been mocked about physics on more than one occasion.  When I am wrong I admit it, because if you don't you can't find the right solution to build that device to get it to work. The truth is more important to me than saving face by having to admit being wrong on the internet.  But, I don't believe that's the way you are operating.  I believe that you will never admit that you are wrong and will carry the fight post after post just to save face no matter what the evidence or argument.  I'm guessing that you enjoy it.  I do not and keep looking for the exit.

I can't see anything wrong to admit to (shrug)

skiing has some very complicated physics going on.  The author of the book on ski physics even told me himself that some things could not be answered very well without computer modeling, because its just too complicated to see all sides, very easy to get trapped in over simplified physics models that lead to incorrect presumptions about skiing.

There is also a significant bio mechanical aspect which is often outside of typical physics analysis.

Personally I think actual ski experience makes it all very self evident.

Quote:
Originally Posted by The Engineer

YAWN!!!!  YM

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