Is an Iron Feruchemist's Energy Conserved? Could the Lord Ruler fly?

[Runetalos]

My question is this. Could someone with the ability to change weight, and the ability to push and pull metal, fly? It would be similar to the way Vin used horseshoes to sort of glide, but wouldn't require ground. This Iron Feruchemist / Mistborn would become light, then push off a piece of metal to shoot forward. Next he/she would become very heavy and pull that metal back (they would be so heavy that the metal wouldn't slow them down). This could be repeated indefinitely, unless momentum is conserved while the Feruchemist is in the air. That is, if this person is flying forward, increasing their weight would need to slow them down if energy is indeed conserved.

[lDanielHolm he/him]

I doubt you can store enough weight for it to work. The anchor needs to be heavier than you to Push off of it (especially if it isn't braced against anything!), but you need to be heavier than the anchor to Pull it to you. I can't remember exact percentages, but I'm certain you cannot reduce your weight below a certain point. I think it would just end up being too close to even your stored weight, so you'd just send yourself and the anchor away from each other, and vice versa when trying to Pull it back.

Increasing your weight in mid-air would slow you down. The same amount of force suddenly has to move a greater weight. Your terminal velocity would be higher, though, so if the force exerted exceeded terminal velocity, you would slow down just a bit less than you would otherwise.

[Straff Venture he/him]

Actually, I think this would work with a horseshoe. When Wax fills his Metalmind, he comments on being buffeted by the wind. In the same situation, a horeshoe would be too heavy to be buffeted by the wind, and we know that Wax can make his weight a LOT heavier than a horseshoe. Therefore he could make himself change weight as needed.

[StormAtlas]

and remember in the second book when Sazed is with Marsh he is able to float like a feather down a cliff

[Teegs]

I doubt you can store enough weight for it to work. The anchor needs to be heavier than you to Push off of it (especially if it isn't braced against anything!), but you need to be heavier than the anchor to Pull it to you. I can't remember exact percentages, but I'm certain you cannot reduce your weight below a certain point. I think it would just end up being too close to even your stored weight, so you'd just send yourself and the anchor away from each other, and vice versa when trying to Pull it back.

Increasing your weight in mid-air would slow you down. The same amount of force suddenly has to move a greater weight. Your terminal velocity would be higher, though, so if the force exerted exceeded terminal velocity, you would slow down just a bit less than you would otherwise.

This statement isn't entirely correct. When increasing your weight, you would no longer be pushing against the horseshoe while flying through the air, therefore only forces acting on you are gravity and drag. When increasing weight, surface area is constant thus drag is constant, gravity is constant, and momentum is increased. Essentially, you were ALREADY slowing down because of drag, HOWEVER the rate at which you slow down is changed. In the case of increased weight, the rate at which you slow down is decreased. Unless you have already reached zero upwards velocity and are already falling. Though I doubt one would want to get to that point to initiate another push off the horseshoe.

My questions is, at what point does the drag force overcome the force of the push. You see, if you decrease your weight to significantly less than the horseshoe and push off the horseshoe in mid air, assuming an entirely elastic situation, you should push off the shoe. However your momentum will be severely decreased, allowing the drag force to slow you at an increased rate. Without actually running numbers I can't say for certain if it would work. What what I CAN say is that if it is possible, it would take some VERY meticulous manipulation of weight and push/pull technique.

Finally, in a vacuum this would work perfectly because there would be no friction to slow you down. Thus, the only force to overcome is gravity.

Let me know if you need clarification on this. I wrote it up pretty quick. =)

[lDanielHolm he/him]

Actually, I think this would work with a horseshoe. When Wax fills his Metalmind, he comments on being buffeted by the wind. In the same situation, a horeshoe would be too heavy to be buffeted by the wind, and we know that Wax can make his weight a LOT heavier than a horseshoe. Therefore he could make himself change weight as needed.

Normal strong wind can buffet someone. A horseshoe generally isn't buffeted by the wind because it has too much mass relative to its exposed surface area.

He most certainly does not make himself as light as a horseshoe. A horseshoe weighs maybe a pound, or two at most. That's maybe 1.3% of an average human adult's body weight; I am certain I've seen Brandon say they cannot store that much.

and remember in the second book when Sazed is with Marsh he is able to float like a feather down a cliff

He doesn't quite float--in fact, the passage makes sure to point this out. He falls, but slower than normal, and since his muscles aren't affected by the loss in mass, and he taps his pewtermind, he lands without injury.

This statement isn't entirely correct. When increasing your weight, you would no longer be pushing against the horseshoe while flying through the air, therefore only forces acting on you are gravity and drag.

An object in motion stays in motion unless acted upon by an outside force. I'm arguing that the increased weight would be that outside force. I wouldn't know how to model this in reality; things don't tend to increase suddenly in weight. Maybe if someone throws a ball so precisely that, while you are flying through the air, you catch it at the apex of its flight?

When increasing weight, surface area is constant thus drag is constant, gravity is constant, and momentum is increased. Essentially, you were ALREADY slowing down because of drag, HOWEVER the rate at which you slow down is changed. In the case of increased weight, the rate at which you slow down is decreased. Unless you have already reached zero upwards velocity and are already falling. Though I doubt one would want to get to that point to initiate another push off the horseshoe.

Surface area is constant, but drag is not dependent solely on surface area. The object's velocity is a factor as well, and velocity, of course, is equal to force divided by mass. Since the object's mass is higher and force is constant...

At least that's how I see it, though my education in physics is not extensive at all.

[Teegs]

An object in motion stays in motion unless acted upon by an outside force. I'm arguing that the increased weight would be that outside force. I wouldn't know how to model this in reality; things don't tend to increase suddenly in weight. Maybe if someone throws a ball so precisely that, while you are flying through the air, you catch it at the apex of its flight?

Surface area is constant, but drag is not dependent solely on surface area. The object's velocity is a factor as well, and velocity, of course, is equal to force divided by mass. Since the object's mass is higher and force is constant...

At least that's how I see it, though my education in physics is not extensive at all.

Increased weight is not a force, gravity is a force, and acts at 9.81m/s^2 no matter what you weigh. You'd need to have a rather large surface area to actually accelerate (and fall) much slower than that (i.e a parachute).

Furthermore, force is mass x acceleration (not velocity). Drag is slowing you down no matter what. A change in mass will affect the rate at which you slow down (acceleration). Drag is a function of surface area, liquid density, object velocity and a drag coefficient. Thus as far as that equation alone is concerned, you can't determine if your velocity will increase or decrease with a change in mass.

Another way of looking at it: Drag exerts a force on you that causes you to “decelerate”, (remember, acceleration is a vector quantity, and it can have positive or negative values depending on the direction of the vector and the way you define your axis. In this case, drag is slowing you down because it opposes your motion; therefore I defined acceleration as a negative quantity. That’s important in terms of balancing your force equations when running calculations.)

Anyway: F=ma -----> a=F/m -------> as “m” increases your acceleration decreases. As “m” decreases your acceleration increases. If “a” is the “deceleration” (negative acceleration) you experience due to drag, increasing “m” will DECREASE the RATE at which you slow down. And if you decrease "m" you will INCREASE the RATE at which you slow down.

This is difficult to explain without pictures, but I don’t have a way of getting anything up while I’m at work. Let me know if I need to break it down some more. =)

[11thorderknight]

The really interesting question (to me anyway) is this: lets say a modern day feruchemist is about to be hit by a car. He taps all the weight stored in his ironmind to momentarily become exponentially heavier. What happens? In theory, the car should not be able to move him, since at the moment of impact, he's many times the car's weight. That means the car has to stop, which means the feruchemist's body just exerted a massive reactive force on the car. What happens to the force imparted to the feruchemist? Does he turn into a really heavy human pancake? Or is he ok because his individual molecules are each too heavy to move, and therefore he can withstand the force of impact?

[dj26792 he/him]

This is actually an ongoing discussion on the forum, and as far as I can remember Brandon has even been asked and said its theoretically possible to fly by this method, but many people, myself included question the ability of even the most gifted of people to pull it off.

In terms of the car crash question, if the feruchemist weighs much more than the car then much less force is imparted to them, and they would probably do fine, if they didn't have enough weight to get sufficiently massive then I suspect it would not go so well for them, although they would also get thrown clear which would make it less damaging... the car crash is complicated. Thats a good answer, the car crash is complicated, someone more interested in physics can run through the various scenarios and work out the optimum weight to be if they wish to, but I can't be bothered.

[Eric]

I think he would actually be hurt worse. Bullet logic: if it hits you and stops, it has imparted all of its energy to your body, maximizing the damage done. If it hits you and goes through (or in the case of the car, if it hits you and you roll with it), you take less damage as energy is expended in the remaining motion.

[dj26792 he/him]

It's a little more complicated than that cause being heavier less of the force of the reaction would hit you, but also yes you would get it all internally rather than externally, but equally being thrown from the impact would do a lot of damage if you were light, I honestly don't know if you'd be better off having maximum mass, minimum mass or mass approximately that of the car, or just slightly either side of the car, its the sort of thing I'd want to run through a computer to calculate all the different scenarios, or ask xkcd to work out for us.

[king of nowhere]

I think it should work.

I'm pretty sure we see some scene in alloy of law where wax changes his wheight in midfly, and he doesn't slow down or accelerate. that means that iron feruchemists are not energy conserved.

flying should however be difficult. you can modify your wheight, but you cannot modify that of your anchor. and you need a heavy anchor to push effectively, so that would drag you down.

However, two iron feruchemists, one of them iron misting, should pull the trick neatly.

they are together, one of them (say A) makes himself heavy and the other (say B ) light, A push B (manually, you don't need allomancy there) who shot forward without A slow much. then B makes himself heavy and A light, and they pull, so A catches up with B. repeat at will.

Edited December 12, 2012 by king of nowhere

[Eric]

It's a little more complicated than that cause being heavier less of the force of the reaction would hit you,

That's not accurate. See the Mythbusters testing their own theory that two cars ramming each other at 50 mph will deal 100 mph worth of damage. The actual result was... 50 mph worth of damage to each car. It averages out across the objects involved, not based on weight. Equal and opposite reactions and all that jazz.

but also yes you would get it all internally rather than externally, but equally being thrown from the impact would do a lot of damage if you were light,

That's part of my point. Being thrown from the impact? That's energy imparted to you being bled off as kinetic energy. It isn't damage to you until you hit something else, but you've already used some of that energy moving through friction/drag and gravity. It's marginally safer to be mobile when struck.

I honestly don't know if you'd be better off having maximum mass, minimum mass or mass approximately that of the car, or just slightly either side of the car, its the sort of thing I'd want to run through a computer to calculate all the different scenarios, or ask xkcd to work out for us. :P/>

You want maximum toughness. Unless you can tap mass to the point where you're skin is tougher than whatever the vehicle is made of, you are on the losing end of the exchange. You could get away with being elastic enough to whether the impacts without abrading or breaking, but I don't know how you'd manage. (Alternatively, start dumping all the speed and warmth you can into metalminds. See if you can't bleed off all the energy from the impact into those and achieve a perfectly elastic impact.)

This has given me the hilarious mental image of a feruchemical engine. Instead of combustion, you have a bunch of feruchemists storing and tapping weight in cycle to turn a motor. (It helps if you imagine each of them as a Buddhist monk.)

And finally, for an on-topic comment, King of Nowhere has answered the first question with evidence, so I'm really tempted to say TLR could fly. Most of the skill requirements would be possible for a Iron/Steel savant (and after being Mistborn for 1000 years, it's entirely possible that he became a savant in every metal he had regular supplies of).

[dj26792 he/him]

That's not accurate. See the Mythbusters testing their own theory that two cars ramming each other at 50 mph will deal 100 mph worth of damage. The actual result was... 50 mph worth of damage to each car. It averages out across the objects involved, not based on weight. Equal and opposite reactions and all that jazz.

Thats true for two cars, but if you get a car and a Road Train the truck doesn't take much damage. the car takes an awful lot more than against another car, the mythbusters thing is not overly relevant, and if what you say is correct illustrates an incredible lack of understanding of basic physics on their part. The mass of the objects is very relevant in the force distribution.

That's part of my point. Being thrown from the impact? That's energy imparted to you being bled off as kinetic energy. It isn't damage to you until you hit something else, but you've already used some of that energy moving through friction/drag and gravity. It's marginally safer to be mobile when struck.

The engergy lost in flight is negligible, the odds of that flight having an extremely unpleasant landing are pretty good, particularly if you actually get knocked flying, arms and legs go everywhere, they break when you land despite the marginally lesser force. My instinct would definitely be that heavier is better, particularly if you can get massively heavier, potentially being massively heavy and picking your feet up at the last second... but that sort of physics isn't really my thing. I'd like to hear from someone better at this sort of physics than me.

You want maximum toughness. Unless you can tap mass to the point where you're skin is tougher than whatever the vehicle is made of, you are on the losing end of the exchange. You could get away with being elastic enough to whether the impacts without abrading or breaking, but I don't know how you'd manage. (Alternatively, start dumping all the speed and warmth you can into metalminds. See if you can't bleed off all the energy from the impact into those and achieve a perfectly elastic impact.)

That would be interesting but I'm not sure how effective it would really be, minor changes to mass would make a much bigger difference, also I think you'd be better off making sure as much of the energy as possible goes into warmth etc cause your bones will break when you hit the ground, you can't really avoid that, unless you get so massive that all of the force went to the car, but that would probably require compounding.

Also, I feel a little out of my depth with this sort of physics its not something I've really studied in detail much. I'm studying to be an engineer, but this sort of stuff hasn't come up in detail yet and I haven't even looked at the basics of it since year 12 physics which was a long time ago. Someone better at physics than me should actually crunch some numbers on this and see what happens.

[Eric]

Force = Mass x Acceleration, yes? So the force should be equal across two bodies colliding (or one body being struck by another). The acceleration will be less to the more massive object, but the force will be identical. And if you're more massive but still squishy, you're going to be more like an immovable foam mattress than a bulwark of strength.

Consider: if you took all the energy that went into breaking limbs and applied it directly to the point of impact, you'd end up with more serious direct trauma and far less secondary trauma. That's exactly what I expect would happen. If feruchemical weight is equivalent to mass, as evidence elsewhere discussed suggests, you're better off storing than tapping. It reduces the force applied to you, and if you pull a Sazed and get to the point where drag has a lot more effect on you, you could bleed off most of the acceleration just fluttering away.

Would storing speed reduce your acceleration from external stimuli? If so, that's the only answer we really need.

Totally agreed on the Mythbusters vs physics, though. That one should have been obvious.

Edited December 14, 2012 by Eric

[Satsuoni he/him]

Ok, people, some points to consider:

1. Remember when Sazed used his weights to stop the gates being hit by Koloss from opening? While that is probably not as much energy as a colliding car, it would still left him broken if his weight was not increased. The damage to the tissues is not done by energy, in the end, it is done by displacements of molecules in the body, and heavier molecules are displaced much less by the same amount of energy.

He became so heavy he felt his own weight crushing him to the ground, and only his increased strength managed to keep him on his feet. Frustrated koloss pounded on the gate, but he held.

2. The iron feruchemists do not conserve energy, unless it is tapped directly from the weight/mass by mc^2. Here is what happens when iron is tapped mid-swing:

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.

Likewise, storing weight mid-flight will drain your kinetic energy.

3. This is a rather strange point, but while iron stores something that seems like mass, it is not quite mass, since your density apparently does not change significantly (alloy of law)

Wax drew every bit of weight he had left, draining his metalminds completely. That was hundreds upon hundreds of hours of weight, enough to make him crush paving stones if he tried to walk on them. In the strange way of Feruchemy, he didn’t grow more dense—bullets would still cut through him easily if they hit.

Which is kind of weird, since the ability to cut also depends on displacing molecules, and may indicate that, like so many things cosmere, weight/mass depends on perception of the objects around him (in this case, whether his body is perceived as a whole or in parts. By the bullet. As I said, strange.)

And to the OP: An iron allomancer/feruchemist (which would incidentally make him a compounder) will probably be able to kind of fly, but it would be awkward at best. Like described above - throw a heavy object away, store, pull yourself toward it, stop pulling, tap weight, slam into object, imparting to it significant excess momentum, store, seeing it fly off, rinse and repeat.

[Eric]

Actually, that last quote proves that adding weight won't protect you from impact. In a weird, physics-ignoring way, but still.

The first quote adds padding, dispersing the energy across a greater area, which prevents damage even in normal situations. This is why a punch from a boxer doesn't pierce right through someone's skull, despite having more energy than 9mm handgun bullets: it's spread across a larger area.

I disagree with your assertion on the second quote. Energy could still be conserved if we read "the weight crashed" as after he "slammed his body". 'He was against the gate and massively tapped weight, which shut the gate,' rather than 'tapping as he hits the gate, causing him to be heavier when he slams into it'.

[Kurkistan he/him]

Just to throw in some points on density: I have my own little crazy-pants theory on density and Iron Feruchemy. Essentially, Wax is just wrong when he says that he doesn't become more dense. It's just that making soft tissue a few times heavier isn't going to do much in stopping a bullet.

I may be struck down by Auotpwail again, but that's my take.

EDIT: If this is the case, then Wax should sink like a stone in water.

Edited December 22, 2012 by Kurkistan

[dyring]

Brandon have mentioned that some of the powers bend/break the laws of physics if you go into detail havent he? They are very logical generally, but weight in particular is abit odd. I agree that wax should get more dense, logically, but I think this is one of the places where Brandon dont quite follow the laws of physics, as its been explained rather often in the book by different people. So I do think he would get killed by a bullet.

Admittedly, it is a possibility that its not be properly tested, its been thought it wouldent help as a bullet have a hellufalot of kinetic energy, so if someone was 10 times as heavy, sure, the bullet only went halfway through the fellow when it would otherwise have gone clearly through and kept on. Not all that often someone makes themselves 100 times or more heavier, wich might have been needed.

Another possibility is that it doesent affect the body at all, all the weightincrease only comes into being at the bottom of your skin. At the point where your body tries to rest the weight so to say. that is is not density thats stored, but the effect upon your surroundings. Would explain it, wouldent it(atleast if my explanation manages to say what I mean;)

I still think its likely that this is one of the times the rules are bent abit, as it is magic ;)/>

Edited December 21, 2012 by dyring

[ustus]

Two things to add here: on tapping weight while in water:

Bouyancy is based on force equilibrium. I.e. you float if the pressure exerted by the water in an upward direction on your body os greater than the force of gravity pulling yoh down (the property we call weight). So if yoh tap weight in water you will, undeniably, become less bouyant. Interestingly enough, this means storing weight will make you more bouyant...

On density:

I beleive the point of wax's quote there is to say that his tissue does not resist stresses or strains any better while he is heavier, as he undeniably has more weight per unit volume. Since density is mass per unit volume, only stresses/strains will be affected by the difference between storing weight and storing mass.

My two cents. Actually, no... my two clearchips.

[Thought]

My questionis this. Could someone with the ability to change weight, and the ability to push and pull metal, fly?

Yes, and we have the word of Sanderson on this:

His concern was getting hit with the counterweight, not the physics of it, and that was just with an Iron Twinborn. With a full twinawesome, it makes perfect sense that we could combine Vin's trick with a proper counterweight (or counterweights) and obtain flight.

The most efficient way would probably be for two twinawesome to work in tandem and serve as eachother's counterweight

Actually, that last quote proves that adding weight won't protect you from impact. In a weird, physics-ignoring way, but still.

Actually, no, it doesn't prove that. Wax said that bullets can still cut him. Cutting and impacting are different things. A diamond is dense, but not necessarily heavy, and a bullet will probably be stopped by it, leaving barely a scratch. In contrast, a ton of cotton candy would be heavy, but not dense. A bullet should go right through it without a problem.

We know that Wax was able to survive a drop of several stories, through floors, by increasing his "weight." Falling even two should have been enough to seriously injure him. The implication here is that his mass would indeed help him survive a car crash.

The oddity comes in that storing "weight" actually stores mass. By increasing his mass, Wax should also be increasing his density (as density a product of mass over volume, and we know his volume doesn't change along with his mass). Yet we know, from comments like the original quote, that he isn't changing his density. Clearly, iron ferrings can control higgs-boson particles in a novel way.

[Eric]

Actually, no, it doesn't prove that. Wax said that bullets can still cut him. Cutting and impacting are different things. A diamond is dense, but not necessarily heavy, and a bullet will probably be stopped by it, leaving barely a scratch. In contrast, a ton of cotton candy would be heavy, but not dense. A bullet should go right through it without a problem.

...Cutting is what you get when the force of an impact is focused on a small surface area. It is 'precision impact'. If there's no discernible difference, then we have proof that there's no discernible difference. For what it's worth, the ton of cotton candy can stop a bullet, because the bullet doesn't have the energy to displace all that mass; shape will determine whether or not the cotton candy does, but it is more than capable of doing so. Diamonds are about 1/3rd as dense as lead, the most common bullet material, and are brittle despite their hardness (i.e., they are structurally weak to sharp impacts, like bullets).

Basically, everything in your paragraph certainly sounds reasonable, but doesn't hold up to scrutiny of the facts.

[dyring]

We know that Wax was able to survive a drop of several stories, through floors, by increasing his "weight." Falling even two should have been enough to seriously injure him. The implication here is that his mass would indeed help him survive a car crash.

Wait, what?

where did this come from? When hes falling to avoid the bomb, its one story and hes stopping himself with a downpush. Where else did he fall with increased weight?

[Satsuoni he/him]

OK, let us consider known facts about Iron Feruchemy and see if we can make them coherent

1. Storing "weight" makes you lighter on your feet and more buoyant. Tapping "weight" makes you harder to move, i.e. you inertial mass at least grows.

2. You are immune to your own Feruchemy. Your body isn't crushed by additional mass, your heart does not explode trying to move blood that is heavier than molten uranium, etc. In fact, the body seems to act like your mass didn't change.

3. Your momentum and kinetic energy grow when "weight" is tapped (see Sazed closing the door, etc)

4. Yet your hardness, and, apparently, viscosity do not change (hardness depends largely on molecular bonds, and is less related to density. Viscosity for normal liquids is often - but not always - proportional to density).

5. As a summary, you apparently get immune to blunt trauma when "weight" is tapped but not cutting or piercing. Whether you get shockwave in your blood (forgot the proper name) from the impact, is unknown.

6. And also, you can move your body when "heavy", but you feel the weight, and after tapping enough "weight" will need more strength to actually walk.

7. Also, mass is the only thing that is increased. Temperature, for example, does not change, which suggests that kinetic energy of atoms/molecules does not change (although temperature is more complex than just kinetic energy).

Ok, so here is the theory to explain all of those points, as far as I can tell:

First, awesome math

Let us define localized density rhol(V) as the mass of the part of the body with the volume V (called localization factor), divided by this volume V and averaged over all (connected?) subsets of body with the total volume V. V can run fro 0+ to total volume of the body.

It is easy enough to see, that for a normal physical body, rhol(V) stays more or less equal for any V. My theory is, that for a Iron Feruchemist that is not so, and when the "weight" is tapped, Feruchemist's rhol starts depending on V (not sure if linearly or not), remaining the same for V near zero, and growing/falling to the full increased/decreased weight/mass.

By this theory, how the action would affect you depends on its locality, which can be iffy to determine, but essentially related to the area of impact for wounds. Therefore, blunt weapons/trauma, with the largest area, are the least effective since they work against much larger total inertial mass (like hitting the bag of platinum sand), and sharp knife is the most effective. The Allomancy (pushing/pulling metals) works against the whole body.

As for the body itself, it always works on the completely local level (V=0), so no changes take place per se. You still have to contend with gravity pull, but not locally. So your body itself moves as if it were in normal gravity, so you can move it as usual. Changing its position (position of the center of mass) relative the planet, however gets harder or easier - you get heavier or lighter at your feet (and do less damage with your fists). In case of Wax raising his arms, according to my theory, he would have to lower/ keep his center of mass - crouch a bit - to do that, but not too much.

Now, onwards to metaphysics, or why would that work like above.

According to my theory in my sig, all connections are stored in Spiritual realm.

That includes gravity and inertial connections, which are spiritual according to Ars Arcanum in WoK. So, when "weight" is tapped, those connections get flooded with energy, but only external connections - those existing outside of your body as it perceives itself. So, when you attempt to move a part of the body, it would be affected proportional to how close it is to being your whole body, with bigger parts gaining generally more mass for interaction.

Mind you, this is just a theory, but unless some other facts that contradict it are forthcoming, I'll stand by it.

[Thought]

@Eric, good point about a diamond's brittleness. I had forgotten to take that into account. However, even though you mentioned the key concepts, you totally missed them. What stops a bullet is hardness and elasticity, primarily. What saves a person in a car crash is mass. That is why you were wrong.

Hardness and other factors are important in a car crash, but the major damage comes from a massive object transferring its kinetic energy to a less massive one. Because of the mass differences, the energy produces more damage. Equalize the masses, and the two objects will fair similarly. Increase the mass on the lesser object significantly, and the damage to it is reduced. Indeed, increase it enough and the damage from this transfer of energy can be largely negated. All the other damage still remains, of course.

Bullets function along the same way. They cause damage by transferring kinetic energy from a more massive object (a lead alloy bullet) to a less massive bit of flesh. But wax can increase his mass, so he can negate that damage to a decent extent. However, bullets cut into the skin, and cutting, though it involves mass, has more to do with hardness, elasticity, etc, which tapping "weight" doesn't influence. Thus, while Wax should be able to survive the punch of a bullet better, they are still going to cut him, they'll still cause him to bleed, etc.

And since we know that storing weight actually stores mass (as flying, which Sanderson confirmed, wouldn't work with weight but does with mass), it makes perfect sense that Wax could survive the impact of a car but still get cut by bullets.

Or, to put is another way, mass should help him endure crushing wounds, but not piercing ones.

Actually, tapping mass should make the bullet a little worse, in that it will definitely transfer all its energy to his body (more massive cells should drag on the bullet more, causing it to slow more, and reduce the chance of it exiting). It might be that storing "weight" would actually help survive bullet wounds, because the bullet it more likely to pass through the body easily, and thereby not fully transfer its energy.

As for cotton candy, interesting idea. I am not entirely sure, though, as you'd have to line up so much cotton candy to create enough drag that I might expect gravity to finish the bullet off first.

@Dyring, you're right. I was almost positive it was several stories, and that he didn't have time to push off anything, but there it is, in the book, otherwise. Though still, we know that Wax changes his mass, so he should still be better at surviving high levels of kinetic energy transfer.

EDIT: Essentially ninja'ed by Satsuoni... by over an hour. I should write faster. At this point, I am fairly certain that storing/tapping "weight" really affects an individual's relation to higgs-boson particles.

Edited January 6, 2013 by Thought