Physics debate

[tkarhu]

You’ve done nothing more than put on a show and demonstrate that which on which we agree: That a skier can apply mass to the front of a ski by shifting weight forward.

Well, the experiment quite clearly shows the difference between a free pivot and a cable. I would also say, an imperfect experiment is better than no experiment at all.

@GrimSurfer Can you provide any evidence for your claims? By evidence, I mean empirical data.

Heel lift power and binding resistance seem not to be opposing forces. Rather, a binding resistance allows some of a heel lift force to be transmitted to the tip of an attached ski. The more resistance, the more force seems to be transmitted. For this reason, it seems difficult to illustrate the forces as vector arrows in a fully realistic way.

Note -- I write ski tip here because "front ski" would not be exact either. At least ski tip is in front of a binding certainly. Further, it seems to even make sense to say that a cable or flexor creates a rotational power because without the piece a rotational force would not be created to a tip of a ski. See free pivot part of the illustration above. It is only one interpretation that word "create" implies a source of energy. Another interpretation could be that create expresses a comparison between two different bindings / systems.

1. The binding, with cable attached, is in tension. This is what creates resistance to boot movement.

2. Whatever mass is transmitted act on the front of the ski. This is because the whole front of the ski (less, perhaps, a bit of the pocket in a cambered ski) is in contact with the ground. The ski is not free to rotate, after all.

3. The mass applied to the front of the ski is the result of pressure provided by the skier’s weight. Nothing else “creates” this mass.

4. The angular distance between the normal force and mass applied by the skier is what creates force.

5. Force is nothing but mass and direction (or vector). This isn’t my definition. This is the accepted definition in physics.

6. Removing one (mass) or the other (vector) results in no force.

@GrimSurfer Would you please check your assumptions 3 and 4? Looks like there are other factors besides skier's weight. Cable seems to affect, how much of the skier's weight is actually transmitted as force to a front ski. This is also what I tried to illustrate earlier.

Still, everyone has their right for personal views. Yet for clarity and a shared understanding, it is good that we have empirical evidence, too. I believe what people show more than what people say.

[GrimSurfer]

My “claim” is quite simple: Skiing conforms to the Laws of Physics.

This is the issue people are challenging.

From this, the irrefutable evidence is that people don’t understand the laws of physics (even though they use terms like “friction”, “tension” and “weight”, all of which are accounted for, and explained, by Newton’s 2nd and 3rd laws)

[tkarhu]

@GrimSurfer I do not think anyone challenges the laws of physics. They just challenge your interpretation of the laws, when there is a mismatch between their own observations and how you interpret the laws.

[GrimSurfer]

@GrimSurfer I do not think anyone challenges the laws of physics. They just challenge your interpretation of the laws, when there is a mismatch between their own observations and how you interpret the laws.

Yeah, they do. Would you like a quote?

As for interpretation, there is more than adequate *explanation* online.

A cable is in tension. That is the term that people use.

What “tension” actually means is that there is a fundamental symmetry of force. When there is a symmetry of force (push-pull), there is no net external force to apply to the ski. This is a textbook example of Newton’s 3rd Law.

There isn’t any torque from the cables either. They freely rotate (save for minuscule frictional forces) around a point on the toe plate.

The skier provides the force by shifting their weight. This is a textbook example of Newton’s 1st (inertia) and 2nd Laws (gravity).

All the cable does, therefore, is help control the skier’s movement. The skier still provides all the force.

Lilcliffy figured everything out for himself very early in the “debate”, probably because he remembered that which he was taught.

https://www.telemarktalk.com/viewtopic ... =40#p54362

[randoskier]

Hi,

I am just starting this new thread so that the “fights” over physics can be discussed in a specific thread and stop derailing other threads. It is really becoming annoying…

Thank you!

Martin

E=mc ² ....or so I'm told.

[tkarhu]

the cables […] freely rotate (save for minuscule frictional forces) around a point on the toe plate

@GrimSurfer Do you still claim a cable binding works just like a free pivot binding? The video seems to show a difference.

[GrimSurfer]

the cables […] freely rotate (save for minuscule frictional forces) around a point on the toe plate

@GrimSurfer Do you still claim a cable binding works just like a free pivot binding? The video seems to show a difference.

I’m tired of having to repeat myself, using different words and diagrams over and over to explain the laws of physics.

If you want to know what I think (and how the laws of physics apply), read the past 40+ pages.

Or don’t.

[tkarhu]

@GrimSurfer You could just answer yes or no.

[GrimSurfer]

@GrimSurfer You could just answer yes or no.

You could just read what’s been posted already. Or you could stay on topic.

All of my arguments have been about NN 3 pin 75mm bindings. I stated this at least twenty times already in this thread, which you would have noticed if you read the thread before commenting.

Does this cable rotate around a pin? (I put arrows pointing to the pivot point)

Why yes, it does. What a frackin revelation.

So to recap…

The cable is in tension. It cannot transmit a net external force as per Newton’s 3rd Law.

The cable freely rotates. It cannot transmit torque. The only force it transmits are frictional forces, which are scant. Newton’s 2nd Law.

But if you want a complete illustration, go to the following post:

https://www.telemarktalk.com/viewtopic ... =40#p54508

[tkarhu]

All of my arguments have been about NN 3 pin 75mm bindings.

You have been writing about a binding standard. It describes the connection between binding and boot. What you write seems to apply to the binding on the photo, but not all bindings of the standard because the hinge mechanism is not part of the NN 3 pin 75 mm standard. Feel free to correct me if I am wrong.

EDIT: If boot bends at a different front / rear point than where the binding hinge is, cable tension changes, when heel is lifted. Then force transmission behavior will be different from free pivot.