Could you send a small metal object into orbit using A-iron?

[Jn819 she/her]

14 hours ago, therunner said:

The part where it is told from external perspective, where we have no idea what she is pulling (or Pushing!) off of.
If someone described what Kelsier was doing in his last fight, people who argue that Mistborn are basically Magneto, but we had his internal monologues to see just how it was to pull it off, and required use of both steel and iron.

Okay, to be fair, Sanderson does like having unreliable narrators in awe of the hero. But this is Sazed. He basically knows about as much about Allomancy as anyone who doesn't have it possibly could (though I'm not sure he knew of Duralumin at the time). And it's not the confusing rapid-fire ball of rage Kelsier did against the Inquisitor, it's an Allomancer moving one object fairly slowly. Sazed knows enough to say "she Pulled the gate off and dodged out of its way" if that is what happened. But that's not what happened and it's not what he said. She continued Pulling it while moving, making it seem "as if it was tethered to her by a chain."

14 hours ago, therunner said:

And that is why I think Vin was using both metals in that scene.

Does it matter whether she was moving herself by Pulling an anchor or Pushing? She was definitely Pulling the gate, and that's the relevant factor here.

14 hours ago, therunner said:

What the hell are you talking about?

Like yes, any force can be broken down into components, but that does not mean tangential forces are not real?

Why do you think rope is taut once in air?  It is because the tension of the rope makes it serve as sort of lever.
I mean, when you are starting to rotate the rope, the objects is being dragged by the rope. You can literally try it at home.

Okay, you "try it at home." Pull a cord taut, then try to use it as a lever. You have made an assertion that is very easy to disprove if you'll just try it.

14 hours ago, therunner said:

You don't seem to understand physics very well.

I got a 5 (out of 5) on the AP Physics test and passed the course with an A. Granted, high school was a little while ago, but I haven't forgotten that much.

14 hours ago, therunner said:

Forget about rope for a second and look at gravity, which is much better analogue. There we have a central force (like in A-Iron) and it is quite well known that you cannot use such force to induce torque.

Ah, I see you think the Moon has nothing to do with the tides, plate tectonics, the rotation of the planet core that produces Earth's magnetic field...

14 hours ago, therunner said:

That only works if the object is already moving, you simply cannot get it to start orbit you that way.
Additionally, your image implies that the object is being continuously accelerated, which is well, not the case.

If it's not being accelerated, why isn't it going in a straight line? Now granted, there comes a point where its rotational velocity reaches a maximum. It's when the "tangential force" is equal to the force of friction acting to slow down the spinning object and they basically cancel out. (Well, the horizontal force tangent to the orbit of the object. There is a vertical "tangential force" too to counteract gravity; the orbit of the object being swung will by necessity be slightly lower than the point it is being swung from.)

14 hours ago, therunner said:

But there is no tether! How many times do I have to say it?
When you have tether you are never dragging the object close, which is exactly what you do with A-Iron. It simply does not work like you are saying.

There is no physical tether, no. That's why the Lurcher has to be skilled at modulating the strength of their Pull to mimic a tether pulled fully taut.

"you are never dragging the object close" not closer to the current position of your hand, no. But you yourself said that when you start swinging something on a rope, the object is being "dragged" (right before the "try it at home" thing). And it is "dragged" closer to the starting position of the hand. The hand has just moved since then.

14 hours ago, therunner said:

Alright, lets take you image then and analyze it then.
Assuming the circle in the middle represents hand span of grown human we can take it at about ~1 meter in radius. Then the trajectory has radius of circa 6 meters. So at any point in the trajectory, the tangential force will be 6x smaller than the force pulling the object towards the center.

Seems a bit larger than it needs to be, cowboys don't spin around with their arms fully extended, they twist their hand around a radius approximately the length of their forearm or less, so that inner circle would be closer to 30cm. But let's play along with your numbers for now.

The rope is pulled tangential to the inner radius (which is why it is never pulled inside). In other words, if you made a line from the center of the orbits to the start of the rope and another from the center to the end of the rope, those plus the rope itself would form a right triangle. How convenient, trigonometry is easy! If we do the math, we find that the angle of the rope to the "tangential force" is the same as the angle of the two radii we made, so yes, the tangential force must always be the same ratio of the total force as the ratio of the radii! You got something right! You get a sticker!

15 hours ago, therunner said:

If you just start a pull at ~10 Newtons, nothing too fancy, the object will hit you in ~1.1 seconds, and no amount of moving your hands about is going to change.

Where did you get its mass? You must have picked one to be able to convert force to acceleration to then take the double integral of the acceleration, set that equal to 6m, and solve for time. (Or use a pre-solved kinematic equation as a shortcut.) After all, a Newton is a kilogram meter per square second (or second squared, though I've always thought that wording leaves ambiguity as to how much of the phrase is being squared). Rounding it, it looks like you assumed a one-kilogram object (or, more likely IMO, just forgot the kg part of N). That is kind of important to know. (In fact, for those who are paying attention, you know that by choosing 1kg and a 10N force, we're already setting ourselves up to fail. We'll get to that.)

15 hours ago, therunner said:

So you have to move to the side. Why am I not considering the centrifugal force? Because it is too small to do anything, even after 1.1 seconds, the speed generated in the tangential direction is tiny. The centrifugal force generated through the movement would be only 0.2, far smaller than the attractive force you are using to drag the object towards yourself. Even taking it into consideration immediately, it would mean still you have to move at ~5 m/s or something like that.

So you have to move, specifically, you have to move in such a way that you maintain the distance to object as constant (or nearly so). So that immediately means you can get object to orbit you only if you are pulling at less than 20 Newtons (in plane) or so, because at that point you have to move yourself faster than humans can move (on their own).

In our scenario, you have to be moving at ~5.45 meters per second. The issue of course is that when you move, it will change what is the centrifugal and what is tangential, in ideal scenario you moved in such a way that the original centrifugal direction is now tangential. You also have to modulate your pulls somehow, but lets not get into that.

Ah yes, if you make calculations assuming that you don't move the proper way to maintain an orbit, the answers show the force you're exerting on the object will accelerate it toward you and it will hit you! Brilliant!

15 hours ago, therunner said:

Now, how fast would the object have to be moving for the image to work?
Well, we know that v^2/r = F. So if you are pulling at measly 10 Newtons, the object has to be moving at ~7.8 meters per second.

This is why working out your units is important, students. Let's look at that a little closer. Velocity squared, then divided by the radius, equals the force. Just looking at the units, that's ((m/s)^2)/m=N, or m/s^2=kg*m/s^2. See why my opinion is that you simply forgot the M in F=MA? But yes, the square root of 60 square meters per square second rounds to 7.746 meters per second. (The hypothetical doesn't assume a limit to the accuracy of our measurements, so we get to use infinite significant figures, but whatever.) Of course, this formula is only valid for things that are moving circularly; suddenly we're assuming we got it to work.

15 hours ago, therunner said:

Which is my entire point, you can use A-Iron to sort of catch an object that is already moving and capture it for orbit. But you cannot induce an orbit.

[facepalm]

15 hours ago, therunner said:

And all of the above still neglects gravity, which would complicate things further (again, the rope does a lot of work).

Yeah, let's fix that.

16 hours ago, therunner said:

Since we are assuming that the Misting has hands apart to get as much tangential force as possible (for some reason, since as I outlined that part is basically negligible), that means they are ~1.5 meters above ground level. (for simplicity)

Why say imprecisely? We're making up the numbers here, let's say you managed to find someone whose arms were precisely 1.500 meters above ground level. Using the same (unnecessarily large, as I said earlier) radii of 1m and 6m, that would mean the object is hanging down about 1m (the angles are the same), so at .500m AGL.

16 hours ago, therunner said:

Part of the pull force has to be counteracting gravity, so right off the bat, Misting must pull more forcibly than 10 Newtons, because 10 Newtons is force of gravity alone.
Assuming the object will be orbiting at ground level, and  keeping  the 6 meter distance, we get that Misting must be pulling at ~24 Newtons only to overcome gravity, leaving 14 Newtons in plane for all the other stuff. You can make the plane force smaller, by bringing the object closer, but then you are losing on the already small tangential acceleration.

And here it is! The moment we've all been waiting for! The point where suddenly the fact that we chose 10N and a 1kg object makes all the difference! Scadrial does have "cosmere standard" (Earth) gravity according to Arcanum Unbounded, so if you remember memorizing that acceleration due to gravity is 9.80 m/s^2, you immediately saw the problem of only pulling with a force that could accelerate the object by 10 m/s^2.

The obvious answer here is not to increase the force, but to reduce the mass to something closer to what Coinshots usually use, say something that weighs about 1N (has a mass of about .1kg), a little under a quarter pound (how much the meat patties at McDonalds weigh). We could be ridiculous and go for the actual mass of a coin, say 1.67g (.00167kg) for a gold dollar, but that would be overkill. While we're changing numbers, let's use some more reasonable radii akin to lassoing. How about an inner radius of 30cm (.30m) and an outer radius of 1.5m? A one to five ratio will make things easier.

We already know what the component counteracting gravity must be: 1N. Looks like centripetal force is 5N this time. 5N/.1kg=50m/s^2=v^2/r and r is 1.5m, so v^2=75m^2/s^2, so v=5*sq.rt.3=8.66m/s. The circumference is 2pi*r = 3pi meters = about 9.42m, so the Lurcher would have to be moving their hand around the inner circle a little less than once per second to stay in sync with the orbiting object. (That's very doable.) Kinetic energy=.5mv^2=.5*.1kg*75m^2/s^2=3.75kgm^2/s^2=3.75J, which isn't a lot. (That's why lassos don't really hurt when they hit.) Also, like with a lasso, the way to get it up to speed is to start slower (and gentler) and go around faster and faster until you reach max. Zane could levitate himself only about a meter over a coin, so it's possible that with practice you could Pull that softly. (Now I want to see a Lurcher with a steel cable lasso lol.)

But the Lurcher would probably be pulling harder on a smaller object. There would be a larger outer radius, a smaller inner radius, or both, and the component counteracting gravity would be a drastically smaller proportion of the total force. They could probably move around their inner circle two times per second with a radius of 10cm, since that's about what a hula hoop takes (as far as movement of your torso where A-Iron lines come from). I'm tired of doing math, but you could get a lot more kinetic energy into it. You might even be able to get it supersonic, like a whip crack.

And again, like with a lasso or swinging something with a rope, all you have to do is start slower and gentler to get it going.

As for usefulness, it's probably not much more useful than Pulling and dodging...as a means of dealing damage. But if you can keep it orbiting around you as a deterrent, like somebody performing a sweeping greatsword kata, it could certainly be worth learning. (Side note, can we agree that Adolin's moment fighting with a greatsword in Shadesmar was pretty awesome?)

[therunner he/him]

I don't think I will continue to engage as I don't really appreciate your personal attacks and condescending attitude. It is okay to disagree and discuss, but I don't enjoy the rudeness.

I did make some mistakes in the post, thank you for pointing them out. I should not post in a rush

On the subject I will only have 3 notes:

1. I said 'sort of lever'. Also, the try it at home was for the fact that rope is pulling the object at the end, and the object starts moving only after the rope becomes taut, not referencing the lever. So again, object at the end of rope will start moving only once the rope is under tension (or taut), before hand it will stay still. You can try this by tying a piece of string to e.g. book, leaving the string loose and then pulling on the string.
2. I don't think the acceleration would work out like you want to, simply because we know that Pulling/Pushing gently is very hard, and here you would have to modulate strength of the pull basically continually. Even if it did, you either have to raise the hand above your head to make the movement or rotate your entire body.
3. I don't think it would work as deterrent, If I would see someone with their hands raised, swinging it around and moving one object, I would not be really scared, more amused.
   Because you could not orbit more than few object like that, and they would all travel in a clump, since they follow the hand.

 

So to even start considering whether it is possible or not, it requires the Lurcher to be able to gently push (which is hard and requires years if not decades of practice) and to move the point they are pushing from to their palm (which we have quite possibly seen only done by someone with literal centuries of experience, and that is not even confirmed).

 

Quote

So again, object at the end of rope will start moving only once the rope is under tension (or taut), before hand it will stay still. You can try this by tying a piece of string to e.g. book, leaving the string loose and then pulling on the string.

That I can agree to.


 

Edited June 5, 2023 by therunner

[Jn819 she/her]

On 6/5/2023 at 4:02 AM, therunner said:

I don't think I will continue to engage as I don't really appreciate your personal attacks and condescending attitude. It is okay to disagree and discuss, but I don't enjoy the rudeness.

My personal attacks and condescending attitude? Okay, I really have to get my side of the story out there. Here's how I see it.

I entered this discussion when people were already disagreeing and talking past each other. I tried to find points of agreement as a baseline so we could see where the disconnect in opinions was. I tried to explain the position I agreed with in another way that might be easier for some people to see. Alder seemed to get pretty close in his reply, stating that "you're just leading the object behind your hand in circles around you, while you spin." (Which is sort of what spinning a lasso is, but he seemed not to get the connection and didn't seem to realize how much smaller the radius of your hand can be to the radius of the object.) CometaryOrbit at least agreed to the first thing I listed as a point we probably all agree on, but had similar trouble seeing the connection between lassos and orbits. I did get a bit aggravated at Alder for nitpicking a hypothetical, but at the time I'm pretty sure I didn't know English was his second language. @alder24 Sorry for snapping at you.

Then you came in and the very first thing you said to me is "That would not work at all." And you ended that first comment by taking my assessment of Alder's physics knowledge and basically saying that I not only didn't know what I was talking about but also hadn't thought things through. I responded by pointing out your errors and trying to explain with the analogy. I even went to a lot of effort to create a diagram that might help. I probably should have taken the high road and not responded at all to your insult, but I was frustrated.

You then repeated your insistence that I was wrong and not thinking things through while using a tone that implied that I was an utter fool for missing something so obvious. My next reply contains no insult or condescension whatsoever and includes a textual reference from Sanderson. Your reply directly contradicted the textual reference, repeated your insistence that A-Iron couldn't transfer "tangential force," made the same mistake as Alder in implying that you'd have to spin exactly as fast and it would follow your hand exactly (as in, with the same radius), called my analogy "flawed at the core," and repeated your insistence that it would only work if the object happened to start with the perfect orbital velocity, again, with a tone and emphasis implying that I was being obtuse.

My reply started by emphasizing the specific point of the textual reference that your explanation most contradicted. I then finally put into my own words what you seemed to be implying, but I thought you couldn't have meant that and therefore was perhaps too expressive of how ridiculous I thought it was. I then granted a partial agreement to the "spinning and it follows your hand" thing while explaining that it didn't have to be the same radius. I was perhaps too dismissive in my reply to your insult. I finished by reiterating how it could work.

In the next comment, your reply on the textual reference was at least respectful enough, though wrong. That's probably the first point in the entire discussion where your tone wasn't disrespectful. And you immediately ruined it by using laughing emojis in response to my explanation. You then insisted that yes, a (taut) rope can "serve as sort of lever" and said I "don't seem to understand physics very well." A timing that I think perfectly highlights the irony of you complaining about my "personal attacks and condescending attitude." You approached respectful again in requesting that we consider gravity again. Then you emphatically repeated your error and added a new one as if I was silly for not seeing it your way. Your reply to my dismissal of your insult was probably only as disrespectful as it deserved. You then went into the math a bit, and you were at least only mildly condescending (I've addressed the errors in math already, no point in rehashing that).

CometaryOribt popped back in (reasonably respectfully) to repeat agreement with you.

My tone was pretty conciliatory on the textual reference in my opinion. I was a bit exasperated with the "try it at home" thing and it shows. I think I demonstrated remarkable restraint in my reply to your insult, but I guess I kinda ruined that by comparing you to Bill O'Reilly. I think my tone in the next section was perfectly fair and reasonable. Same with a couple following that. I might have been a little too sarcastic with everything I used exclamation points for, but considering how frustrated I was getting, I'm glad I kept myself from going further. Similarly, I think [facepalm] is an entirely appropriate response to claiming that math which assumes we got it to work proves it doesn't work. I spent a while expanding on my diagram for you. The rest of that comment was fairly conciliatory.

Your last response here is still pretty dismissive, but it raises a couple of relatively fair points. Let's get to those then, shall we?

On 6/5/2023 at 4:02 AM, therunner said:

1. I said 'sort of lever'.

Where's the fulcrum? Where is force being exerted in the opposite direction from the force at the end of the rope? I'm sorry, but if you get to call my analogy flawed, this is a really flawed analogy. The rope is not pushing anything, only pulling.

On 6/5/2023 at 4:02 AM, therunner said:

Also, the try it at home was for the fact that rope is pulling the object at the end, and the object starts moving only after the rope becomes taut, not referencing the lever. So again, object at the end of rope will start moving only once the rope is under tension (or taut), before hand it will stay still. You can try this by tying a piece of string to e.g. book, leaving the string loose and then pulling on the string.

Yes, obviously. I wouldn't want to mistreat a book like that though lol. Think of swinging something small (let's say wired earbuds) around your head. You start by holding it up off the ground. The wire is under tension, it's just that all of the tension is counteracting gravity; the wire is straight vertical. You then start moving your hand around in a circle, and the tension increases as it no longer has to just counteract gravity. The tension grows as a larger proportion of it must be converted to centripetal and tangential force. At full speed, the component counteracting gravity will be much smaller than the centripetal force. That said, yes:

On 6/5/2023 at 4:02 AM, therunner said:

Pulling/Pushing gently is very hard, and here you would have to modulate strength of the pull basically continually.

I think how difficult it would be to modulate the strength depends a lot on how the perception of iron lines works. If you can see just with iron lines like Inquisitors do, it stands to reason that you can tell how far away something is and in what direction it is just by the line. You should be able to do a trial-and-error kind of thing and pull harder when the object starts moving further away and either move faster or pull softer when it's coming closer. It would still take a lot of practice, though.

On 6/5/2023 at 4:02 AM, therunner said:

Even if it did, you either have to raise the hand above your head to make the movement or rotate your entire body.

I don't think that would be a significant factor in the difficulty here. Since iron lines are described as letting you see all around yourself, you wouldn't actually have to change which direction you are facing, you could just do a hula hoop movement. And semantically speaking, that is revolution (like what makes a year), not rotation (like what makes a day). If you would, please use the appropriate terminology for the sake of clarity.

On 6/5/2023 at 4:02 AM, therunner said:

I don't think it would work as deterrent, If I would see someone with their hands raised, swinging it around and moving one object, I would not be really scared, more amused.
Because you could not orbit more than few object like that, and they would all travel in a clump, since they follow the hand.

Perhaps you don't have the same experiences I do. I grew up with two brothers who liked roughhousing. Swinging something around so fast that it whistles certainly makes people stop and think before diving in for the attack.

On 6/5/2023 at 4:02 AM, therunner said:

So to even start considering whether it is possible or not, it requires the Lurcher to be able to gently push

Pull, but I get the point so no big deal

On 6/5/2023 at 4:02 AM, therunner said:

(which is hard and requires years if not decades of practice)

Difficult but not impossible yeah, since Zane was about Vin's age (around 20). (It's possible his spike strengthened his A-Steel though, as hers strengthened her A-Bronze.)

On 6/5/2023 at 4:02 AM, therunner said:

and to move the point they are pushing from to their palm (which we have quite possibly seen only done by someone with literal centuries of experience, and that is not even confirmed).

Again, the hula hoop movement is a viable alternative. I do agree that we can't be sure (yet) that you can Pull from a different body part though.

[cometaryorbit]

Zane's spike did boost A-Steel.

[therunner he/him]

On 12/06/2023 at 5:24 PM, Jn819 said:

My personal attacks and condescending attitude? Okay, I really have to get my side of the story out there. Here's how I see it.

Yes yours, you started with condescension and continued quite liberally.

On 12/06/2023 at 5:24 PM, Jn819 said:

Where's the fulcrum? Where is force being exerted in the opposite direction from the force at the end of the rope? I'm sorry, but if you get to call my analogy flawed, this is a really flawed analogy. The rope is not pushing anything, only pulling.

Yes, rope is pulling object in tangential direction, one you cannot get with A-Iron.
Lever can both push and pull, depends on how you use it, so the analogy is sound.

Once more, gravitational system is the best analogy for A-Iron, with only central force.

On 12/06/2023 at 5:24 PM, Jn819 said:

Yes, obviously. I wouldn't want to mistreat a book like that though lol. Think of swinging something small (let's say wired earbuds) around your head. You start by holding it up off the ground. The wire is under tension, it's just that all of the tension is counteracting gravity; the wire is straight vertical. You then start moving your hand around in a circle, and the tension increases as it no longer has to just counteract gravity. The tension grows as a larger proportion of it must be converted to centripetal and tangential force. At full speed, the component counteracting gravity will be much smaller than the centripetal force. That said, yes:

Yes, and the wire of the earbuds pulls the earbuds.
And it pulls them tangentially to start their revolution, not normally towards you.
You don't get earbuds to revolve around you by pulling earbuds towards yourself, which is what A-Iron does.

On 12/06/2023 at 5:24 PM, Jn819 said:

I don't think that would be a significant factor in the difficulty here. Since iron lines are described as letting you see all around yourself, you wouldn't actually have to change which direction you are facing, you could just do a hula hoop movement.

Yes you would. If you are pulling from your hand, and your hand drives the movement (which again I dispute would work), then you need to move your hand in circle around your body. Hence, your body has to rotate.

Quote

And semantically speaking, that is revolution (like what makes a year), not rotation (like what makes a day). If you would, please use the appropriate terminology for the sake of clarity.

I was using proper terminology, no need for further condescension.

Your body would have to rotate, not revolve. Rotation is around axis going through body, revolution is around axis outside of body.

On 12/06/2023 at 5:24 PM, Jn819 said:

Perhaps you don't have the same experiences I do. I grew up with two brothers who liked roughhousing. Swinging something around so fast that it whistles certainly makes people stop and think before diving in for the attack.

I have quite comparable experience.
All you need is throw e.g. rug over them. Or have armor.

On 12/06/2023 at 5:24 PM, Jn819 said:

Difficult but not impossible yeah, since Zane was about Vin's age (around 20). (It's possible his spike strengthened his A-Steel though, as hers strengthened her A-Bronze.)

As cometaryorbit pointed out, his A-steel was strengthened.

Edited June 25, 2023 by therunner

[The Stormfather He/Him]

with two coinshots you might be able to make it orbit around the earth.

Both would need extensive amounts of stored sight, and mental speed.

One would push it up, and another would push it away from far off in the world, making it move at a sharp diagonal.

You would need probably two fullborn to do this well, and with much iron counpounding for more powerful pushes.