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Effects of Iron Feruchemy


ulyssessword

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I haven't been able to pin down exactly what changing your mass by using Iron Feruchemy does, but I've gotten close. The three main questions I have are what happens to your mass/weight, strength, and motion.

Mass/weight

Iron Feruchemy affects mass, and does not affect the acceleration of gravity. The increase in mass would lead to you pressing harder on the floor, but would not make you fall faster (discounting air resistance). This is pretty much confirmed in a few places.

Strength

From AoL Ch. 6

Taking a deep breath, Waxillium flared his steel and tapped his iron metalmind. Filling it made him lighter, but tapping it made him heavier—much heavier. He increased his weight a hundredfold. There was a proportional increase in the strength of his body, or so he’d guessed, as he didn’t crush himself with his own weight.
This seems to suggest that increasing your mass increases your strength by a proportionate amount, but it would negate the logic behind lowering your mass to make yourself lighter on your feet, as below (AoL prologue):
He often went about at three-quarters of his unadjusted weight, making himself lighter on his feet, quicker to react.
The only way I could see this working is if he was referring to being able to push off of lighter objects, as opposed to physical reactions.

Motion

I think that velocity (or speed) is conserved instead of momentum. This seems to fit best with what is written, with 100 fold increases or decreases in mass not resulting in instantly stopping or shooting off wildly in one direction; the problem I have with this is that it breaks conservation of momentum, and can change the motion of an otherwise closed system. This would require creating energy, which goes against the principles of Feruchemy.

I think I pretty much have the mass/weight part down, but what are your thoughts on motion and strength from Iron Feruchemy?

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Well, these things are written from the perspectives of the characters, and Wax isn't a physicist.

As regards the strength, I think the key part of that first quote is "or so he'd guessed". I think strength is the wrong word for him to be using, as it's pewter that deals with strength. (Both for allomancy and feruchemy.) Case in point, Sazed during the defense of Luthadel.

I'm thinking that, in addition to making himself heavier, it's also making himself more dense. After all, his volume isn't increasing, and feruchemy doesn't affect the planet's pull on him, so the only other option that I can immediately see is an increase of density. (A cubic inch of iron is heavier than a cubic inch of tin, after all.) If we ever see an iron ferring in a body of water, this would help verify this theory. Increased density would probably add to his durability, which would coincide with his comment about not crushing himself with his own weight.

I'm not sure about the motion part yet. I thought I remembered a part where Wax was moving very fast and then tapped his metalmind, almost instantly stopping himself, but I couldn't find it.

To continue (without making a point yet; I'm just "thinking out loud"), there was that point in chapter 6 where Wax Pushed himself off the balcony with decreased weight, increased it to Push the chandeliers out of the way, decreased it again to Push himself some more, and farther. That makes it sound like altering his weight (Is that even the right term to use? Shouldn't we use mass?) also altered his trajectory, which was why he had to keep switching between tapping and filling, as well as repeatedly Pushing himself. That would mean that his velocity (speed + direction of travel) would be affected by the use of his metalmind

... Yeah, no. I still don't have an explanation for the motion part.

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Interesting thoughts. I completely agree on the mass, and it makes sense that everything increases or decreases in mass together (or, as darniil put it, density). This is a critical difference between it and pewter; storing pewter only makes you weaker, so your body has more difficulty with vital functions (your heart doesn't pump as strongly, your diaphragm struggles, etc.). Storing iron, on the other hand, makes your blood lighter as well, so although your heart is weaker, it is pushing less massive blood (and your diaphragm is pushing/pulling on less massive lungs).

However, somewhat because I agree on mass, I disagree on the velocity/momentum issue. Velocity is distance/time. That doesn't include mass. I believe it must be momentum that is conserved. I suspect the reason Wax doesn't shoot off wildly is that he's had a lot of practice. My guess is that, with proper timing, you could tap iron, increasing your mass and strength, then jump, then start storing iron immediately, and go flying. But in doing that, you're not going to have much control over your trajectory. In Wax's case, he can use allomantic steel to achieve about the same effect. However, if he is ever deprived of his steel (a leecher attacks, or he is held captive), we might see such a trick.

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I think I may have it. Brandon has talked about the Realmantic nature of Windrunning (which is manipulation of Gravity) before. Let me see if I can find it...

Here it is! It's in the Ars Arcanum of WoK

"A Basic Lashing involved revoking a being's or object's spiritual gravitational bond to a different object or direction. Effectievely, this creates a change in gravitational pull, twisting the energies of the planet itself. A Basic Lashing allowed a Windrunner to run up walls, to send objects or people flying off into the air, or to create similar effects.

Advanced uses of this type of Lashing would allow a Windrunner to make himself or herself lighter by binding part of his or her mass upward."

I think it is this sort of manipulation of Spiritual Energy that is happening with Iron.

My Crazy Idea for explaining Iron is as follows:

In Physics, there is a Gravitational Constant. It's the number that's used to calculate Gravity for the whole universe. It's something like 6.6*10^-11. What if, when Wax is "storing weight" he's reducing that number just slightly for all the particles connected to him so that the world doesn't pull on him as much. When he's "drawing out weight" he's increasing that number so that the world pulls on him a little more.

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Thanks for the feedback, I agree 100% on mass = density, it is true by definition. This also solves the strength issue for me, as increasing your mass would lead to increased "toughness"(resistance to force, including the force of gravity that would crush you), but not increased "strength" (the ability to move things, either your body or things outside of it). This fits with both of the examples, as well as working logically.

The problem that I have with momentum being the basis of motion is that it would require the frame of reference to constantly change in order to not have a bunch of unintended side effects, a couple of examples:

1. You are standing on the equator of a planet that is spinning such that the velocity of the surface is 1,674.4 km/h East relative to an outside point (it's oddly like Earth in that way). You tap an Iron Metalmind, becoming 100x as massive for 5 seconds. During this time, you maintain your momentum, and are now travelling at 16.744 km/h East relative to a point that is not rotating. This sends you West (on the world) at a rate of 1657.656 km/h relative to the rest of the planet. If unimpeded (and no air resistance etc...), you will travel about 2.3 km, or roughly a mile and a half, to the west in those 5 seconds. This can be done in the reverse direction by filling the metalmind instead of tapping it.

This is an absurd example, the reference point (if it is momentum) would need to be the surface of the planet to avoid things like this (or worse the farther away you put the point). The next example is much more likely to happen

2. You are standing inside of a train that is going 100 km/h North (it's faster than most, but it's a math train, so it's OK). You fill your metalmind, becoming 3/4 as massive. To maintain momentum, you are now going 133.3 km/h North as opposed to the train's 100 km/h. This sends you towards the front of the train at a speed of 33.3 km/h, or roughly sprinting speed.

I also found some quotes, but none of them are very illuminating.

From WoA ch. 53 pp 679 (paperback) Emphasis added throughout.

The koloss realized what he was doing too late. He kicked another body out of the way, then slammed his body against the open door and tapped his ironmind, drawing forth the weight he had stored within it. Immediately, he became far heavier, and that weight crashed against the gate, slamming it closed.
This seems to suggest that he was using the increased mass for momentum in addition to grip. He then continued to use the increased mass for grip to finish pushing it closed and keep it there.

I couldn't find any good quotes from Sazed's fight with Marsh or anywhere else, but there are a couple in AoL.

From Ch. 1:

He dropped a bullet casing, and his Allomancy pressed it down onto the rooftop beneath him. He Pushed more forcefully on it, launching himself up and through the swirling mists. He decreased his weight dramatically and pushed on a window latch as he fell, positioning himself so he landed right in the middle of the alleyway.
Unless he started filling it at exactly the peak of his jump, he would shoot to the ground if momentum was conserved, so this suggests that it is velocity.

Ch. 6:

He dashed forward in a crouch and leaped onto a large serving platter. He pressed one foot against the lip of the platter, and Pushed on the bullets behind him. The maneuver threw him forward in a skid across the polished wooden floor. He broke out of the tables into open space just before the steps out of the room, then kicked the platter out from under him and increased his weight, hitting the ground and stopping.
This one seems to support momentum, but it could just as easily have been attempted to be used for grip (which wouldn't work, as the coefficient of friction would be unchanged).

Another from Ch. 6:

Waxillium threw himself off the balcony. As soon as his feet were free, he tapped his metalmind and drew forth as much weight as he could. That didn’t tow him to the ground; an object fell at the same speed, no matter its weight. Only air resistance mattered.

However, weight did matter a great deal when Pushing—which Waxillium did, throwing everything he had against the chandeliers. They ripped apart in a line, the metal inside them twisting upon itself, crystal exploding outward in a shower. That gave him plenty of room along the upper portion of the room to jump in an arc toward Wayne.

In a heartbeat, Waxillium stopped tapping his metalmind and started filling it instead, decreasing his weight to almost nothing. He Pushed on the broken harp behind, and a simultaneous quick Push against the nails in the floor kept him high.

The result was that he soared across the room in a graceful arc, passing through the space the large chandeliers had occupied. The glittering smaller chandeliers continued to shine on either side of him while crystal showered beneath, each tiny piece splintering the light into a spray of colors. His suit coat flapped, and he lowered the single revolver in his hand as he fell, pointing it at the bandit standing over Wayne.

I think that this is fairly strong evidence that momentum is not conserved. He pushed with a huge amount of force against the chandeliers, enough to break off an entire row of them, but did not go shooting backwards when he decreased his weight to normal. I don't think that his push against the harp would be enough to counteract that much momentum.

In conclusion, I think that velocity is conserved, even though it could have more problems than momentum.

NOTE: this was written before reading zas678's post. In response to it: Iron Feruchemy affects mass, not weight. Changing the gravitational constant would result in having more gravitational acceleration (so you would press to the floor harder, and fall faster, which is directly contradicted in the previous quote), but not more mass (aka inertia. It is resistance to acceleration, such as from steelpushing against another object.)

Edited by ulyssessword
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In response to it: Iron Feruchemy affects mass, not weight. Changing the gravitational constant would result in having more gravitational acceleration (so you would press to the floor harder, and fall faster, which is directly contradicted in the previous quote)

Like this?

Instead, he began to fill the ironmind, letting it suck away his weight. He felt a familiar sense of lightness- a sense that his own body wasn't pressing upon itself as forcefully. His fall slowed. The Terris philosophers had much to say on using an ironmind. They explained that the power didn't actually change a person's bulk or size-it just somehow changed the way that the ground pulled against them. Sazed's fall didn't slow because of his disease in weight- it slowed because he suddenly had a relatively large amount of of surface exposed to the wind of his fall, and a lighter body to go with it.
WoA 107, emphasis mine.
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Nope, I think the philosophers Sazed is referring to are wrong there :) . Slower falling could be explained by reduced mass (or density, which is a better way of saying the same thing), for an example, think of dropping a balloon vs. a cannonball. Quotes:

AoL Ch. 6: (emphasis added throughout)

Waxillium threw himself off the balcony. As soon as his feet were free, he tapped his metalmind and drew forth as much weight as he could. That didn’t tow him to the ground; an object fell at the same speed, no matter its weight. Only air resistance mattered.
Direct contradiction with Sazed's quote, but this is an "it is" statement, instead of an "other people say that..." statement. Even with the unreliable narrator, I put more value in it.

From WoA ch. 53 pp 679, also in my last post.

The koloss realized what he was doing too late. He kicked another body out of the way, then slammed his body against the open door and tapped his ironmind, drawing forth the weight he had stored within it. Immediately, he became far heavier, and that weight crashed against the gate, slamming it closed.
Weight cannot "crash against" anything, only mass can.

WoA Ch. 58, pp 747

Marsh immediately tried to Push Sazed away by the metal bracers on his arms. Sazed was ready, however, and he tapped his ring ironmind - drawing forth the weight he had stored within it. His body grew denser, and he felt its weight pulling him down, his fists feeling like balls of iron on the ends of lead arms.

Marsh immediately lurched away, thrown violently backward by his own Push. He slammed into the back wall, a cry of surprise escaping his lips. It echoed in the small, domed room.

Another direct contradiction, as gravitational force and density are not related at all. Also, Marsh pushed against Sazed's arms hard enough to be "addled" when he hit the wall. Only having more grip against the floor would not prevent Sazed from being thrown a near equal distance (or more, as Marsh is presumably bracing himself somewhat), added mass is required.

WoA Ch. 58, pp 747-748

[sazed] snatched the lamp out of the air, then tapped iron hard - increasing his weight manyfold - and tapped pewter to give himself massive strength.

Marsh didn't have time to react. He was now Pulling on a lamp held in Sazed's inhomanly strong, inhumanly heavy, hand. Again, Marsh was yanked by his own Allomancy.

Same argument as above, but he is tapping Pewter as well, which counters some of it if he is bracing/leaning slightly.

HoA ch. 78, pp 677

Tapping weight increased the density of his body and of his bones, keeping him from damaging himself as he collapsed on top of the soldier.
From Sazed's fight with the kandra guards. Another reference to "density" which, as noted above, is related to mass, not gravity.

HoA ch. 78 pp 678

[sazed] slammed the hammer down on a kandra shoulder, growing heavier to add to the momentum of the blow.
Unless he was swinging the hammer very oddly, the effect of added weight would only be to add the weight of his arms to the blow, added mass would allow a more efficient swing (with no need to brace against its momentum) in addition to both weight and momentum of his arms. I don't think it would be worthwhile for just weight.
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With all those quotes, I'm convinced on the mass vs. weight issue. In response to Zas's quote, I believe the latter part explains itself with regards to velocity vs. momentum:

Sazed's fall didn't slow because of his disease in weight- it slowed because he suddenly had a relatively large amount of of surface exposed to the wind of his fall, and a lighter body to go with it.

It would be like turning him into a human-sized balloon filled with normal air. Such a balloon will fall, because it is denser than air, but it will do so slowly, because the difference in density will have a hard time overcoming the air resistance. He essentially makes his terminal velocity very low, and so, even though he was traveling more quickly before, he adjusts to terminal velocity for his new density.

HoA ch. 78 pp 678

[sazed] slammed the hammer down on a kandra shoulder, growing heavier to add to the momentum of the blow.

Unless he was swinging the hammer very oddly, the effect of added weight would only be to add the weight of his arms to the blow, added mass would allow a more efficient swing (with no need to brace against its momentum) in addition to both weight and momentum of his arms. I don't think it would be worthwhile for just weight.

Remember, as we have seen with Wax, it also adds to your strength. Even if he did conserve momentum, temporarily slowing him, gravity's (constant) acceleration multiplied by his increased mass means he would hit with more force, and his increased strength (due to the increased density) would compensate for any initial slowing.

From WoA ch. 53 pp 679 (paperback) Emphasis added throughout.

The koloss realized what he was doing too late. He kicked another body out of the way, then slammed his body against the open door and tapped his ironmind, drawing forth the weight he had stored within it. Immediately, he became far heavier, and that weight crashed against the gate, slamming it closed.

This seems to suggest that he was using the increased mass for momentum in addition to grip. He then continued to use the increased mass for grip to finish pushing it closed and keep it there.

Again, increased strength to physically push against the ground and into the door, and, if he's leaning against it, the increased force from gravity*mass will mean he is pulled down and, because he is leaning toward the door, sideways at the same speed, but with more force on the door.

From Ch. 1:

He dropped a bullet casing, and his Allomancy pressed it down onto the rooftop beneath him. He Pushed more forcefully on it, launching himself up and through the swirling mists. He decreased his weight dramatically and pushed on a window latch as he fell, positioning himself so he landed right in the middle of the alleyway.

Unless he started filling it at exactly the peak of his jump, he would shoot to the ground if momentum was conserved, so this suggests that it is velocity.

Terminal velocity could explain the slowing (even if momentum initially hastened his fall), and he may have pushed on a window latch below him, compensating for his temporary increase in velocity.

Zas, this is completely unrelated, but shouldn't your title be Quoter Extraordinaire, with the extra "a"?

Edited by Musicspren
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From Ch. 6

He dashed forward in a crouch and leaped onto a large serving platter. He pressed one foot against the lip of the platter, and Pushed on the bullets behind him. The maneuver threw him forward in a skid across the polished wooden floor. He broke out of the tables into open space just before the steps out of the room, then kicked the platter out from under him and increased his weight, hitting the ground and stopping.

This one seems to support momentum, but it could just as easily have been attempted to be used for grip (which wouldn't work, as the coefficient of friction would be unchanged).

That's the one I was looking for. I thought it was in chapter 6, but now I see why I missed it when I was looking for it - I was only looking for "tapped" and "tapping", which weren't used in that passage.

Despite that, though, I'm leaning towards the conservation of velocity. IANAPhysicist, so I can't refute your arguments against conservation of momentum. (So I'm hoping you're being honest and accurate, and not a clever troll. :D )

Also, your comment on that passage reminded me of a joke one of my physics professors told us.

Q: Two cats are on a roof. One fell off. Which one stayed on?

A: The one with the greater μ.

@Musicspren: Keep in mind, "strength" is the wrong term to use. Strength is the purview of pewter. Regardless of how Wax uses the term, he's not making himself stronger. (Nor is anyone else who only taps an ironmind.)

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I partially agree, darniil.

AoL Ch. 6

[Wax] increased his weight a hundredfold. There was a proportional increase in the strength of his body, or so he’d guessed, as he didn’t crush himself with his own weight.

Pewter would increase your strength without increasing your weight, allowing you to move better. Allomantic pewter, which works similarly to tapping feruchemical pewter, allows Vin and Kelsier to run much more quickly than normal people could, because they are stronger while their bodies are no more difficult to move. Tapping iron would not allow you to run any faster, because your increase in strength is only enough to compensate for the greater mass. But in the incident with the gate, compare a person running into you at 3 m/s and a chasmfiend running into you at 3 m/s. Both are traveling at the same velocity, but it's probably going to be worse for you when the chasmfiend hits you. When Sazed is pushing to close the gate, he is like the chasmfiend (okay, probably not that massive, but you get the idea) traveling at 3 m/s; no faster, but far more forceful because of his increased mass and strength to compensate.

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It probably would be more damaging to have the chasmfiend hit me, rather than a person, but possibly because of trampling - which isn't a factor in the current discussion, I know - or because of its larger size (volume). So, instead of a chasmfiend, maybe a 5' tall schoolkid and a 7' tall pro wrestler? (Would that be a better ratio?)

(More thinking out loud follows.) 100 pounds of pressure can be damaging or not damaging, depending on the surface area over which it's spread. That's how people can lay down on a bed of nails without being punctured - 100 pounds over a large area, versus 100 pounds over the area of the point of a single nail.

3 m/s. Okay. Over the area of a nail, I'm pretty sure it would puncture my skin. Over the area of a 5' schoolkid, assuming I've done my math right, that kid might knock me over if I'm not bracing for it. Likewise, the wrestler. All three are traveling the same speed, of course, but the wrestler takes up the most volume, so he hits me over a much larger area.

What about a 5' tall adult male professional bodybuilder? Same height as the schoolkid, but larger volume (more muscle), and also more dense. He very likely would knock me over at that speed, maybe even if I were bracing for it. This comparison is a little closer to the differences between an iron ferring when s/he is tapping an ironmind or not. Admittedly, it's not perfect;

in his heyday was considerably stronger than my nephew. :P

Let's get back to that gate. How was the scene set up? The gate swung in, towards Sazed? Let's use that setup, even if I'm remembering the scene wrong. So we've got a gate. It's not locked, but there's something blocking it from the other side, and we want to push the gate open. Someone on the other side has two options for obstructing the gate: one is a block of standard concrete that's 24 ft3 in volume (6'x2'x2'). The other option is a block of aerated concrete of the same volume. The first is more dense than the other, and would be more difficult to move out of the way by pushing against the gate.

You're right, though, that Sazed was more forceful when tapping his ironmind than he was not tapping it; his acceleration may have remained the same, but his mass increased with the tapping.

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I believe that the "increased strength" from tapping an ironmind (finally found an unambiguous way of saying it!) is material strength (how much force it takes to break something), as opposed to physical strength (how much force you can exert with your body).

Musicspren, if I understand correctly, you are saying that the ability to move your body remains constant whether tapping or filling an ironmind (this would be due to physical strength increasing proportionally with mass). I don't think that that is the case, examples/analysis below:

(AoL prologue, also in first post)

[Wax] often went about at three-quarters of his unadjusted weight, making himself lighter on his feet, quicker to react.
As noted in my first post, this would not make you any faster to react (with your body, Allomancy is another matter) if it had a proportionate decrease in physical strength as well.

WoA Ch. 58, pp 747-748

[sazed] snatched the lamp out of the air, then tapped iron hard - increasing his weight manyfold - and tapped pewter to give himself massive strength.
If iron gave increased physical strength as well, pewter would not have been necessary. Not a very good example, but it helps to show how iron would make pewter redundant if it gave physical strength as well.

In Sazed's fight with the kandra guards (HoA ch. 78, pp 677), he had iron but no pewter. If iron let you move your body at the same speed as normal, punching and kicking would have been much more effective than falling, as your fists/feet travel faster than a drop of 5 feet gives.

Iron feruchemy is also described in a couple of places (WoA Ch. 58, pp 747, AoL Ch. 6, WoA ch. 12, pp 124/125, among others.) as feeling light or heavy to the feruchemist. If you gained physical strength along with density/mass, it should not feel any different to you.

Edited by ulyssessword
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Good points; you've come close to convincing on that. One more objection ("There's always another..."):

[Wax] increased his weight a hundredfold. There was a proportional increase in the strength of his body, or so he’d guessed, as he didn’t crush himself with his own weight.

He raised his guns high over his head to keep them out of the radius, then Pushed outward from himself in a ring.

I don't know how much mass Wax's arms normally have. Suppose they are three kgs each (that's probably conservative). Now he multiplies his mass by a hundred. His arms are thus three hundred kgs. Each. Raising three hundred kgs of arm plus a gun "high over his head" with each arm is not going to be possible without adding to his physical strength at least somewhat. He would still feel heavy; just because he has enough strength to overcome it doesn't preclude him feeling the added weight. However, to back up your point:

WoA Ch. 58:

Sazed struggled to step forward, but the pressure of Marsh's Push--along with his own bulky, weighed-down body--made walking difficult

I have as hard a time reconciling this quote with my argument as I have reconciling the previous quote with yours.

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Now for motion, I am fairly sure that it is velocity that is conserved, because of the many exceptions that are required for momentum conservation to not seem completely broken. In addition to the two examples before (my second post, 5th in total), here's a new one, that illustrates the need for yet another exception.

You are jogging at 10km/h, while at 1.5x normal density. At this point in time, your right foot is on the ground (going 0 km/h) and your left foot is reaching forward for the next step (going 20 km/h). Your arms are similar, with your left arm staying still relative to the ground, and your right arm travelling forward at 20 km/h. You suddenly fill your ironmind, reducing your density to 1/10 of normal. This increases the speed of every part of your body 15 fold (to maintain the same momentum). Your right foot (and left arm) is still going 0 km/h, but your left foot (and your right arm) are now travelling at 300 km/h. Similar things happen with your blood travelling faster etc... Because of this, you explode into a feruchemist mist, scattered over the next few kilometres of road.

I see three possibilities regarding this situation:

a) This is literally how it works, but despite never mentioning it to the reader, Sazed and Wax both take precautions to avoid this, such as slowly increasing/decreasing density, and stopping moving as much as possible. Not very likely at all.

b)This is not how it works, because although momentum is conserved for your entire body compared to the outside world (a reference point that is convenient to you, like in the train example), there are special rules for what happens within your body, which prevents this. I don't like it, as it adds unnecessary complexity.

c) Velocity is conserved, not momentum. Can be understood intuitively, even if it breaks (Earthly) physics more.

Iron is also sometimes used in the middle of a swing or charge, which would be counterproductive if momentum is conserved, as it would slow down the motion. Also, Iron Feruchemy is never used as an alternative (or in addition to) to steel's speed for fast travel, as I'm pretty sure Sazed would have figured out/known the trick below (which works with momentum, but not velocity conservation.)

Jog (5 m/s) at normal weight, and jump, similar to a longjump. Decrease your density to 1/10 as much immediately after jumping, increasing your velocity to 50 m/s, angled slightly upward. Maintain this for about a second as you are in the air, then go back to full density as you land. Jog 1 or 2 more steps to regain balance and recover the lost momentum from air resistance, then repeat. This allows travelling about 5x as fast for the same effort, which can be further boosted with steel and pewter Feruchemy or increasing your mass above normal on the ground, albeit at a slight loss due to increased drag.

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Good points; you've come close to convincing on that. One more objection ("There's always another..."):

[Wax] increased his weight a hundredfold. There was a proportional increase in the strength of his body, or so he’d guessed, as he didn’t crush himself with his own weight.

He raised his guns high over his head to keep them out of the radius, then Pushed outward from himself in a ring.

Hmm, I was almost thinking I had a pretty airtight case for each of the three questions, oh well, what fun would that be ;) ? I can't think of any good way to reconcile this with my theory, but here goes anyways:

1) The 100 fold figure could be hyperbole from an unreliable narrator. His mass could be as high as 30-50x normal or so without it being impossible for a strong person to do. This would still be difficult, even considering that a large part of the weight is near the shoulder/core muscles, so it would take less effort to lift than dumbbells (as good of a comparison as we can get here on earth).

2) Him lifting his guns above his head happened at the same time as him tapping his ironmind, and it was narrated in that order because it would be disjointed to the reader if it was described in any other order.

There are huge problems with these, most notably that they both rely on the assumption that what was written wasn't what happened. Some combination of the two is possible, even though it doesn't necessarily take any time to tap or fill a metalmind, he may have taken it. #2 is especially weak, as it would have said "He had raised his guns..." if it was the case.

I'm still in support of material strength without physical strength, but not as sure anymore.

Edited by ulyssessword
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Good work you two, you've convinced me that Iron Feruchemy is a huge mess that shouldn't work at all. It's clear at least that it doesn't directly affect gravity's influence. That strength increase from Iron tapping was a lot easier for me to accept before I had to start thinking about it. There's too much evidence for me to believe it isn't happening. As to why Iron-filling makes Wax a bit faster on his feet, maybe it's not so much for speed as manuverability? Could it be that he'd run at about the same speed either way, but turning/dodging/climbing/jumping is much easier?

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As to why Iron-filling makes Wax a bit faster on his feet, maybe it's not so much for speed as manuverability? Could it be that he'd run at about the same speed either way, but turning/dodging/climbing/jumping is much easier?

If physical strength is directly proportional to change in mass, then it should not make you any faster or slower no matter how much you tapped or filled an ironmind.

This can be seen by applying Newton's second law of motion (force = mass * acceleration, or f = ma). Rearranging the formula, you can get (acceleration = force / mass), which is what we are looking for. Doubling (or reducing by 1/4, or increasing a hundredfold) would not change the acceleration. Calculations:

For a standard person, at a point in time while jumping

Force = f = 2000 Newtons (random number, I have no idea what a good one is)

Mass = m = 100 kg (Wax put on some weight)

Acceleration = a = ??? m/s^2

a = f/m

a = 2000 N / 100 kg

a = 20 m/s^2

For a feruchemist at 1/10 normal mass (with proportional physical strength), at the same point in time while jumping

Force = f = 200 Newtons

Mass = m = 10 kg

Acceleration = a = ??? m/s^2

a = f/m

a = 200 N / 10 kg

a = 20 m/s^2

For a feruchemist at 5X normal mass (with proportional physical strength), at the same point in time while jumping.

Force = f = 10000 Newtons

Mass = m = 500 kg

Acceleration = a = ??? m/s^2

a = f/m

a = 10000 N / 500 kg

a = 20 m/s^2

As you can see, it would not make you able to move faster, as every bit of strength that you gained would be countered by the resistance of moving it, and every bit of freedom you gained from lower mass would be countered by lost strength. I think it would work well with Allomancy though.

Edited by ulyssessword
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I like your most recent discussion of velocity vs. momentum, but I have a thought experiment to counter yours.

Suppose you're fighting something (let's call it the RAFO Monster), and you want to punch it. If storing iron does not affect physical strength, you could begin by storing mass and punching more quickly than usual. Whether or not that works, right before impact, you could tap your ironmind and increase your mass a great deal. If the velocity of your punch is constant and your fist alone suddenly has a mass of several kgs (not to mention the rest of your mass behind it), the amount of force will be extraordinary and the RAFO Monster will, to paraphrase how you so eloquently put it, "explode into a mist, scattered over the next few kilometres."

The increase in energy alone does not bother me; storing and tapping brass (warmth) clearly represents a change in the amount of energy; it comes out balanced in the long run, but in the short run, when you only see the storing or tapping, energy is lost or gained.

But that ability to super-punch (or kick, or whatever) gives an extremely powerful ability to Wax.

Perhaps the moral of all this is that when you use feruchemical iron, someone or something ends up exploding into a mist, scattered across the next few kilometers.

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Suppose you're fighting something (let's call it the RAFO Monster), and you want to punch it. If storing iron does not affect physical strength, you could begin by storing mass and punching more quickly than usual. Whether or not that works, right before impact, you could tap your ironmind and increase your mass a great deal. If the velocity of your punch is constant and your fist alone suddenly has a mass of several kgs (not to mention the rest of your mass behind it), the amount of force will be extraordinary and the RAFO Monster will, to paraphrase how you so eloquently put it, "explode into a mist, scattered over the next few kilometres."
Nah, you wouldn't be able to splatter a RAFO Monster over a few kilometres, maybe two or three rooms, max. It wouldn't be much worse than being hit by a fast moving train. (Weak argument alert!) Thankfully, I don't think that anyone on Scadrial has figured this out, or else there would be a lot more people scattered over the landscape. By my reading of a couple situations, it has been shown to work, albeit used in a much less extreme way. I'm recycling quotes here, but pretty much every example of iron Feruchemy is in this thread already.

From WoA ch. 53 pp 679

The koloss realized what he was doing too late. He kicked another body out of the way, then slammed his body against the open door and tapped his ironmind, drawing forth the weight he had stored within it. Immediately, he became far heavier, and that weight crashed against the gate, slamming it closed.
Sazed was running at the gate, and tapped iron just before hitting it with his body, otherwise his weight wouldn't "crash" into it. Pretty weak, but it's the best I have.

HoA ch. 78 pp 678

He stopped filling his ironmind, regaining normal weight, then reached with blurring speed to pick up the hammer of the fallen soldier. He didn't have enhanced strength, but he had speed. He slammed the hammer down on a kandra shoulder, growing heavier to add to the momentum of the blow.
I think that this is an example of your thought experiment (but less extreme, and only one half of it), and that he tapped the ironmind in the middle of the swing, but it could have been at the start too.

I think that it is a consequence of conservation of velocity, but I don't think it will ever show up. There are some more things that would work with conservation of velocity, but would never show up in a book. If they did, I imagine it would go something like this:

Free energy (aka perpetual motion): Wax is trapped by a koloss tribe, and they will only release him if he can make their windmill turn, so they can grind bones to make their bread (that's what koloss do, right?). Unfortunately, the only problem with it is that there is no wind on it, as it was built underground. The koloss confiscated his Guns, Germs, and Steel, stripping him of his colonial powers, and leaving him nothing but his wits, metalminds, and oddly enough, a physics textbook that Wax "traded" to him. Reading the book, he quickly sees a solution, and ties two or three hundred pounds of weight to one of the blades of the windmill (koloss build things well, very, very well). Climbing out to the end of the opposite blade, he taps his ironmind, increasing his weight tenfold and forcing it to drop to the ground and lift the counterweight. As he swings past the bottom, he starts filling his ironmind, allowing the counterweight to pull the other side down and bringing him to the top, where he begins tapping his ironmind again, swinging over the top and repeating the process. The koloss are grateful, and lock him in a train bound for civilization.

Introducing momentum to a (otherwise) closed system: Wax is trapped inside of a locked train car, again with nothing but his wits, his metalminds, and the physics textbook. The traincar is not attached to any other cars, as the Vanishers unhitched it while stealing the rest of the train. Wax desperately needs to move, but knows that he would need to push off of something outside to move the car, but has no steel to burn. He sketches the problem on the walls, complete with Wayne's mistwraiths and stickmen, then comes up with a solution. He stands at the back of the car, fills his metalmind as much as he can, then heaves himself forward as fast as he can. While in midair, he taps as much weight as possible and lands, shoving the train along the nearly frictionless rails a small amount. He then repeats this dozens of times, and gets the train car going fast enough (about walking speed) to go along the tracks and follow the Vanishers' path. Unfortunately, they switched the track behind them, and it now leads to an abandoned factory.

Flying: Wax is trapped in the basement of an abandoned cannonball factory (it was abandoned because of lack of demand, nobody had invented the cannon yet), still with nothing but his wits, his metalminds, and the physics textbook. The stairs are broken, but the hole from the falling train car is directly above him, from which he can reach the surface. Remembering how he moved the train before, he grabs two cannonballs, one in each hard. He then raises them above his head, fills his ironmind, and jumps while pulling the cannonballs down towards his waist. The cannonballs weigh nearly as much as his body, so he pulls himself up off of them. When they are level with his shoulders, he taps iron, and becomes more massive, stopping them at waist level. He then pulls the cannonballs up from his waist, not losing any speed because he is so much more massive than they are. When they are at his shoulder level again, he fills his ironmind, and lets the cannonballs tow him upward before repeating it again, and again, and again.

Edited by ulyssessword
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HoA ch. 78 pp 678
He stopped filling his ironmind, regaining normal weight, then reached with blurring speed to pick up the hammer of the fallen soldier. He didn't have enhanced strength, but he had speed. He slammed the hammer down on a kandra shoulder, growing heavier to add to the momentum of the blow.

I think that this is an example of your thought experiment (but less extreme, and only one half of it), and that he tapped the ironmind in the middle of the swing, but it could have been at the start too.

This does sound like it. It could be explained with conservation of momentum also, but it can be taken to much more of an extreme with conservation of velocity.

Free energy (aka perpetual motion): Wax is trapped by a koloss tribe, and they will only release him if he can make their windmill turn, so they can grind bones to make their bread (that's what koloss do, right?). Unfortunately, the only problem with it is that there is no wind on it, as it was built underground. The koloss confiscated his Guns, Germs, and Steel, stripping him of his colonial powers, and leaving him nothing but his wits, metalminds, and oddly enough, a physics textbook that Wax "traded" to him. Reading the book, he quickly sees a solution, and ties two or three hundred pounds of weight to one of the blades of the windmill (koloss build things well, very, very well). Climbing out to the end of the opposite blade, he taps his ironmind, increasing his weight tenfold and forcing it to drop to the ground and lift the counterweight. As he swings past the bottom, he starts filling his ironmind, allowing the counterweight to pull the other side down and bringing him to the top, where he begins tapping his ironmind again, swinging over the top and repeating the process. The koloss are grateful, and lock him in a train bound for civilization.

This seems very reasonable if we assume conservation of velocity. It could be modified to work, albeit much less efficiently, with conservation of momentum.

Introducing momentum to a (otherwise) closed system: Wax is trapped inside of a locked train car, again with nothing but his wits, his metalminds, and the physics textbook. The traincar is not attached to any other cars, as the Vanishers unhitched it while stealing the rest of the train. Wax desperately needs to move, but knows that he would need to push off of something outside to move the car, but has no steel to burn. He sketches the problem on the walls, complete with Wayne's mistwraiths and stickmen, then comes up with a solution. He stands at the back of the car, fills his metalmind as much as he can, then heaves himself forward as fast as he can. While in midair, he taps as much weight as possible and lands, shoving the train along the nearly frictionless rails a small amount. He then repeats this dozens of times, and gets the train car going fast enough (about walking speed) to go along the tracks and follow the Vanishers' path. Unfortunately, they switched the track behind them, and it now leads to an abandoned factory.

Also reasonable, although Wax may get a bit too tired before the car can build up enough momentum.

Flying: Wax is trapped in the basement of an abandoned cannonball factory (it was abandoned because of lack of demand, nobody had invented the cannon yet), still with nothing but his wits, his metalminds, and the physics textbook. The stairs are broken, but the hole from the falling train car is directly above him, from which he can reach the surface. Remembering how he moved the train before, he grabs two cannonballs, one in each hard. He then raises them above his head, fills his ironmind, and jumps while pulling the cannonballs down towards his waist. The cannonballs weigh nearly as much as his body, so he pulls himself up off of them. When they are level with his shoulders, he taps iron, and becomes more massive, stopping them at waist level. He then pulls the cannonballs up from his waist, not losing any speed because he is so much more massive than they are. When they are at his shoulder level again, he fills his ironmind, and lets the cannonballs tow him upward before repeating it again, and again, and again.

I don't think this one works. If we assume physical strength is constant and velocity is conserved (as you do), he could simply jump while at low weight and be propelled high into the air. If we assume momentum is conserved and physical strength is proportional to mass (as I do), he could jump while tapping his ironminds, then immediately start filling ironminds, and fly off. Either way, he can fly without cannonballs.

One thing neither of us has considered is the possibility that there is a delay in changing the extent of tapping or storing. That is, maybe he can't immediately go to being near-weightless or a hundred times his weight; even a few seconds of delay could make many of these cases impractical. It also means that the explosion into a feruchemist mist might not occur with conservation of momentum, because the change in mass wouldn't be instantaneous.

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A small counter to the super-punching of the RAFO Monster (great name :D), you should not be able to instantly (in a very short time) switch between light/fast and heavy, and the potential energy in the speed of the punch would probably be used up by whatever process causing the change.

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