Physics debate

[GrimSurfer]

The bottom line here is that anyone who has ever used a three pin binding without the optional cable for K&G will immediately feel tip pressure as soon as you put the cable on and take a kick. Once you feel it, the science behind it is obvious.

And you were doing so well before, when you mentioned the front of the ski…

Because, when the ski is compressed, the forward most contact point is nothing more than that. It’s not like you can direct your mass to that exact point like Yoda. You’re putting weight (or mass) onto the ski.

Let me frame this differently though… in terms a downhill skier might better understand.

Downhill skis are pretty flat. They don’t have the uncompressed camber that a XC ski does. When the boot is in the binding, where do you think forward pressure from the skier goes? It is distributed along the front portion of the ski that is in contact with the snow.

An XC ski isn’t all that different. When compressed, the contact area of the ski is pretty much it’s entire effective length (less, perhaps, part the pocket on some skis). More so on a single camber ski, which is what you have quite correctly stated in the past gives a better XCD experience.

So all this talk about *tip* (which isn’t in the official FIS vocabulary… yes, I checked) doesn’t accurately describe what is going on with the ski.

[Stephen]

@GrimSurfer , it seems like we are maybe getting too hung up on words here.
Honestly, I am probably more picky about using words and terms accurately than most.

While you can rightly call out the factual distinction between the tip of a ski; and the front of a ski, and the part of the ski in front of the binding toe piece pivot point, and the shovel of a ski, and etc.
Is it possible you might seek to understand how your fellow forum members are using the terms and then look for a bridge to understanding?

So, if some, ANY force is applied to the part of the ski that is in front of the binding pivot point, then SOME of that force will get to the end (what some may call the tip) of the ski, with the zero point being to line where the front of the ski curves up, and leaves the snow.

Does this seem accurate to you, or do you see it differently?

[DG99]

I see, the original problem was probably this bit (which hypothesis has since been abandoned):

“Nope. This would violate the laws of physics.

The cables do not impart any force themselves. The push on the back of the boot is exactly the same as the push on where they attach at the binding. Those forces are equal and opposite, exactly as Isaac Newton specified in his Third Law of Physics. They balance out. The net force is ZERO.

The cable controls heel movement, helping the foot rotate in one plane. It is that rotation that shifts body weight forwards or backwards over the length of the ski. This affects the force directly applied to the ski through the sole of the boot by the body (specifically, whichever points are in contact with the ski).”

[Stephen]

I see, the original problem was probably this bit (which hypothesis has since been abandoned):

“Nope. This would violate the laws of physics.

The cables do not impart any force themselves. The push on the back of the boot is exactly the same as the push on where they attach at the binding. Those forces are equal and opposite, exactly as Isaac Newton specified in his Third Law of Physics. They balance out. The net force is ZERO.

The cable controls heel movement, helping the foot rotate in one plane. It is that rotation that shifts body weight forwards or backwards over the length of the ski. This affects the force directly applied to the ski through the sole of the boot by the body (specifically, whichever points are in contact with the ski).”

Maybe.
Good find in all this!
But trying to glue all the piece together via text seem to be a challenge.

[GrimSurfer]

I agree with your description @Stephen

When people say other things, like *tip of the ski* or *ski tip*, one must assume that this is what they mean to say. I mean, “along the front of the ski” isn’t so difficult to type, is it?

I look at this discussion in the context of the recent endeavours of @wabene (who has participated in this discussion on occasion). He’s new to telemarking and is practicing prior to receiving lessons in a week of so…

In another thread, @wabene mentions going over his tips a few times. We’ve all done this at some point, and it’s a sign of being waay too far forward on our skis.

Now if you misunderstand the discussion on torque and weighting the *tips* or your skis, @wabene may be left wondering wtf is going on. After all, haven’t some people here said that you need to weight the tips of skis? Sure they have… and if that is what @wabene is taking literally, then he needs to thank these folks for helping him have a face plant. At least it’s not a collar bone…

This is why we need to be very careful in our descriptions and explanations. This is a sport, so injury can occur… or people can just become frustrated because they think they’re unable to do it.

That’s why “understanding” is so important.

[GrimSurfer]

I see, the original problem was probably this bit (which hypothesis has since been abandoned):

“Nope. This would violate the laws of physics.

The cables do not impart any force themselves. The push on the back of the boot is exactly the same as the push on where they attach at the binding. Those forces are equal and opposite, exactly as Isaac Newton specified in his Third Law of Physics. They balance out. The net force is ZERO.

The cable controls heel movement, helping the foot rotate in one plane. It is that rotation that shifts body weight forwards or backwards over the length of the ski. This affects the force directly applied to the ski through the sole of the boot by the body (specifically, whichever points are in contact with the ski).”

If you can point out how cables impart a force on the ski without violating the laws of physics, I’m all ears….

[Stephen]

I agree with your description @Stephen

When people say other things, like *tip of the ski* or *ski tip*, one must assume that this is what they mean to say. I mean, “along the front of the ski” isn’t so difficult to type, is it?

I look at this discussion in the context of the recent endeavours of @wabene (who has participated in this discussion on occasion). He’s new to telemarking and is practicing prior to receiving lessons in a week of so…

In another thread, @wabene mentions going over his tips a few times. We’ve all done this at some point, and it’s a sign of being waay too far forward on our skis.

Now if you misunderstand the discussion on torque and weighting the *tips* or your skis, @wabene may be left wondering wtf is going on. After all, haven’t some people here said that you need to weight the tips of skis? Sure they have… and if that is what @wabene is taking literally, then he needs to thank these folks for helping him have a face plant. At least it’s not a collar bone…

This is why we need to be very careful in our descriptions and explanations. This is a sport, so injury can occur… or people can just become frustrated because they think they’re unable to do it.

That’s why “understanding” is so important.

Maybe we are making progress!
I don’t want to detract from that, but would offer another explanation for:

In another thread, @wabene mentions going over his tips a few times. We’ve all done this at some point, and it’s a sign of being waay too far forward on our skis.

This is most likely due to deceleration, and associated with the lack of heel retention telemark bindings (don’t) have.

[wabene]

Your right GS that I'm just learning the turn. I think it's @mca80 that's getting the ski lessons up on Da UP! I doubt you could even get tele lessons around here, . That's alright, I'm hooked and I'll keep plugging away. Just taking a day off as I can barely move after a big weekend of skiing.


Edit: Geez Louise, I cannot believe this discussion continues... the endurance exhibited is remarkable

[DG99]

I see, the original problem was probably this bit (which hypothesis has since been abandoned):

“Nope. This would violate the laws of physics.

The cables do not impart any force themselves. The push on the back of the boot is exactly the same as the push on where they attach at the binding. Those forces are equal and opposite, exactly as Isaac Newton specified in his Third Law of Physics. They balance out. The net force is ZERO.

The cable controls heel movement, helping the foot rotate in one plane. It is that rotation that shifts body weight forwards or backwards over the length of the ski. This affects the force directly applied to the ski through the sole of the boot by the body (specifically, whichever points are in contact with the ski).”

If you can point out how cables impart a force on the ski without violating the laws of physics, I’m all ears….

It’s a springy lever system

Oh… maybe you’re pointing out that the cables at rest don’t move by themselves, but rather just sit there unless some outside force imparts some kind of Newtonian force to them?

[GrimSurfer]

I see, the original problem was probably this bit (which hypothesis has since been abandoned):

“Nope. This would violate the laws of physics.

The cables do not impart any force themselves. The push on the back of the boot is exactly the same as the push on where they attach at the binding. Those forces are equal and opposite, exactly as Isaac Newton specified in his Third Law of Physics. They balance out. The net force is ZERO.

The cable controls heel movement, helping the foot rotate in one plane. It is that rotation that shifts body weight forwards or backwards over the length of the ski. This affects the force directly applied to the ski through the sole of the boot by the body (specifically, whichever points are in contact with the ski).”

If you can point out how cables impart a force on the ski without violating the laws of physics, I’m all ears….

It’s a springy lever system

Oh… maybe you’re pointing out that the cables at rest don’t move by themselves, but rather just sit there unless some outside force imparts some kind of Newtonian force to them?

The cables are in tension. Whatever force is applied to them in one direction is equal to the force in another direction. Why. Because both ends are fixed to the same object.

There is only one outside force at play… gravity. The rest are just internal forces — weight (of the skier), friction (of the ski) and drag (skier’s coefficient)… if one excludes thrust (from poles).