Physics debate

[GrimSurfer]

If Isaac Newton skied, he'd be telling you that cables create force. He'd probably wonder if you were dropped on your head.

STRICTLY speaking, cables to not CREATE force.
This is where we have been hung up all along.
They do TRANSMIT force, which is what I belive you mean, and is what I UNDERSTAND you to be saying.
If I have that wrong, please feel free to flame me!!!!

It’s starting to dawn on some people that cables don’t create force. This represents progress… if only in one more person than it did yesterday.

Things are still hung up the transmission of force because people haven’t been able to shake themselves of the opinion that a cable, attached to itself through a plate (of sorts) can transmit additional force. The cable is in tension. The force that it creates in one direction (against the heel) is equal to the force it receives in another (against the cable by the plate). So the net force is zero.

This is why cables can’t create force, which is something @Stephen now understands.

The tension of the cable is resisted by the boot. The differing arcs of the cable-plate and boot-plate creates variable tension throughout a range of motion.

The amount of force that the skier is able to provide by moving their mass doesn’t change. Merely the response. The only thing the cable does, therefore, is facilitate control. It doesn’t provide any force because it doesn’t create it.

You can’t give that which you do not have. This is a very elementary way of stating the problem. But it might get people over the hump reconciling tension and the application of a net force, which are two different things altogether.

[TheMusher]

You’re rewriting the script.

Nobody thinks the cables create forces per se, merely that they transmit force - a concept you have been opposed to as per my recent quotes.

Think you should stop lecturing - even dragging people down - and humiliating yourself in the process.

[GrimSurfer]

You’re rewriting the script.

Nobody thinks the cables create forces per se, merely that they transmit force - a concept you have been opposed to as per my recent quotes.

Think you should stop lecturing - even dragging people down - and humiliating yourself in the process.

No. I’m not rewriting the script. Merely repeating it.

See the post by @Stephen that I quoted (and the one where @lowangle al used the word “create”). It’s all written down for you…

[lowangle al]

I'm sure I know how a cable binding works and how it relates to tip pressure. I know how to apply that tip pressure to my skiing. I don't need to know anything else, no additional info will change my skiing.

[lowangle al]

You’re rewriting the script.

Nobody thinks the cables create forces per se, merely that they transmit force - a concept you have been opposed to as per my recent quotes.

Think you should stop lecturing - even dragging people down - and humiliating yourself in the process.

No. I’m not rewriting the script. Merely repeating it.

See the post by @Stephen that I quoted (and the one where @lowangle al used the word “create”). It’s all written down for you…

The cable doesn't create the force, lifting your heel does. If you don't lift your heel then the cable does nothing.

[GrimSurfer]

If Isaac Newton skied, he'd be telling you that cables create force.

The cable doesn't create the force, lifting your heel does. If you don't lift your heel then the cable does nothing.

Progress, even when measured by the angstrom, is still progress.

Lifting a heel, without shifting mass, doesn’t do anything. Shifting mass can be done without lifting a heel, but this eventually leads to a loss of balance.

Therefore, one must ask if lifting a heel applies force or whether it simply facilitates the weight shift needed to maximize the amount of force applied to the front of the ski through the ball of the foot?

The correct answer is obviously the latter.

[lowangle al]

This really doesn't have anything to do with weight shifting. When you lift the heel it puts tension on the spring, which wants to lighten your tail there by loading the tip. It's simple stone age technology, a lever.

[DG99]

Meh. It’s no big deal to insist things like the cable transmits rather than creates force. Or the very tippy tip doesn’t actually get pressured. Just some physics related semantics.

Meanwhile some various severe misunderstandings are occurring like regarding the free pivot on the Voile Switchback. And the real mystery of why cable and/or bumper resistance is helpful hasn’t been solved.

[tkarhu]

Perhaps one of the physics-inclined members, or @GrimSurfer himself, can draw and post the free-body diagram of forces at play. I think it would really summarize the discussion well and perhaps give everyone a visual representation of the forces and dynamics between the snow surface, ski, binding, boot, and body.

Here is a try to illustrate the forces (image below). It is more an "artists' interpretation" than a free-body diagram though I guess.

(original image by @lilcliffy)

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 front part 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.

[GrimSurfer]

Meh. It’s no big deal to insist things like the cable transmits rather than creates force. Or the very tippy tip doesn’t actually get pressured. Just some physics related semantics.

It appears to be semantics until conclusions are applied to the real world.

If people take nonsense about cables seriously, they may conclude that their inability to perform certain manoeuvres is about their equipment. Maybe they need a different cable? That doesn’t work… maybe they need a cable with a different spring? Or a different pair of boots…

This creates a circle of confusion that ultimately goes nowhere.

But if we regard the cable as a control mechanism, rather than a force bearing element, then any failure becomes one of technique.

That helps guide advice away from playing equipment “whack-a-mole”, which has become a bit of a sport onto itself.