Conservation of Momentum

[Galladon]

This is just a nice obeservation: Brandon gives a nod to conservation of momentum (p) at the end of the book. As Wax remarks that he gains a burst of speed when starting to fill his metalmind while in motion.

 

Basic Law is that the sum of all impulses within a system must remain the same from time t1 to time t2 (under ideal conditions). 

 

If we apply this to p=m1 (mass at t1) * v1 (velocity at t1)  an say he decreases his mass m2 = 1/2* m1 then follows => that v2 =2 * v1.

 

So very nice little integration of real world physics there Mr. Sanderson this is why I love your books

[RShara]

Except he's decreasing his weight, not his mass, otherwise his density would change, which it doesn't. 

[Khyrindor]

Actually he does decrease his mass. I think it was just confirmed this week. I'll try to find it.

 

EDIT: Found it.

 

 

Q: Metalminds: if you store weight, how does that work, do you decrease your mass?

A: Storing weight actually plays with your mass, because if you look at how we do the physics of it… This one is really screwy. Because we are changing mass and playing with it… [Wax example] There is conservation of momentum and stuff like that, but how can you store your mass… Well, in the magic system it works, but it’s one of the weirdest things we do. We kind of play loose and free with the physics sometimes. Like the ee do the physics of it… This one is really screwy. Because we are changing mass and playing with it… [Wax example] There is conservation of momentum and stuff like that, but how can you store your mass… Well, in the magic system it works, but it’s one of the weirdest things we do. We kind of play loose and free with the physics sometimes. Like the example that I often cite is Wayne doing a speed bubble, I choose to make light from inside not get a redshift. We kind of look at what is good storytelling first, and then work the physics around it.

 

 

Source:

https://docs.google.com/document/d/1TDoKTQciZ3CIdo3IKc8N9fILHfJDeSvo2DEPtvEQPzY/edit

Edited October 13, 2015 by Khyrindor

[RShara]

Well if he says so.  It doesn't make sense with density, though

[Khyrindor]

I think Brandon also said that it doesn't affect the density, although Sazed had said otherwise.

[Voidus]

Weight is weird feruchemically, it does affect density in some ways (Otherwise wax would have crushed himself many times over by now) but not exactly as you'd expect so I take it as one of those things that Brandons obviously thought about but there's a little bit of handwaving going on when you get right down on the specifics.

[Galladon]

The thing is that sure under normal circumstances decreasing the density would be the only obvious way to decrease mass:

Problem 1 changing density simply means altering the chemical composition (decreasing the atomic numbers) which wouldn't make sense, or thorwing out all the neutrons which would make it seriously unstable and only allows for a weight decrease of 49.9999...% (e-).

So this means changing the mass withou toughing density:

 

This can be achieved by either manipulating the local Higgs field (change the amplitude) or reducing the number of Higgs boson particles whithin the atomic structures. This seems like the most likely candidate for influencing mass.

[FirstSelector]

As a technical note, the overwhelming majority of mass of protons and neutrons comes from the binding energy of the quarks, not the interaction with the Higgs field.

 

But in any case, strictly speaking changing mass while keeping volume constant does change the mass density.  What it (probably) doesn't change is the number density, which is to say that a Skimmer modifies the mass of her constituent particles, not how many particles she is made of.  This distinction is important because various material properties (tensile strength, for example) will depend on these quantities in different ways.

 

For various reasons, I think much of the physics and chemistry would carry over if Skimming changed the mass of the protons and neutrons, with a few adjustments to things like bodily tensile strength to prevent gravity from ripping apart the Skimmer.

Edited October 14, 2015 by FirstSelector

[+Authweight]

I think the easiest way to understand what's happening is that "weight" is a cognitive idea, while mass is a physical property. So when Wax stores weight, the cognitive action is simple, but then the physical world is made to do some real gymnastics to catch up to what Wax sees himself as doing.

Edit: This doesn't really tell us much about conservation of momentum though. It sounds like what's going on is more complex than a simple change in mass equivalent to the weight change.

Edited October 27, 2015 by Authweight

[fyodor]

This conservation of momentum contradicts a few examples from other books, where momentum is not conserved

 

In WOA Sazed closes a gate by leaping towards it and increasing his mass mid-jump

In AOL Wax knocks down a door by jumping towards it and increasing his mass

In the AOL building destruction scene Wax launches himself into the air and significantly increases his mass but suffers no loss in speed.

[natc]

For the last one, did he actually stop his push?

Doors in general: not sure whether momentum even matters in those situations. You're looking to reach a certain amount of force against the door on impact here. You'd come to a stop right after anyway.

[fyodor]

Wax had stopped pushing. He pushed into the air once and then increased his weight tremendously, without any loss in speed. While he is zooming up he then pushes against the roof, but because of his significantly increased mass the kickback doesn't slow him down and he keeps moving through the hole created in the ceiling. Speed, not momentum is conserved.

 

Similarly, if momentum were conserved Sazed would find himself slowing down after he leapt at the door and his leap against the door wouldn't push through the Koloss.

 

Similarly, Wax wouldn't be able to knock the door open if momentum was conserved. It's only by throwing himself at the door, increasing his mass, and using his heightened mass and conserved speed that he hits the door with enough momentum. If you put on a backpack with 200lbs of weight on it, you wouldn't suddenly be able to knock down doors. 

Edited October 28, 2015 by fyodor

[Stormgate]

I refer to the Ars Arkenaum in the back of the book, the part that says there is an effect when Allomancy and Feruchemistry are used at the same time. Wax's is that he apparently gets faster. Wayne's is likely that he heals faster, or something like that.

Basically, I'm explaining Wax's increase in speed by saying, "magic,"

[Ari]

I refer to the Ars Arkenaum in the back of the book, the part that says there is an effect when Allomancy and Feruchemistry are used at the same time. Wax's is that he apparently gets faster. Wayne's is likely that he heals faster, or something like that.

Basically, I'm explaining Wax's increase in speed by saying, "magic,"

 

It actually doesn't exactly say that. It says there's an effect beyond the interaction of the two powers, a "perk," for each type of Twinborn, similar to the perks of the Knights Radiant, like Shallan's ability to take Memories.

[coppercloud]

It actually doesn't exactly say that. It says there's an effect beyond the interaction of the two powers, a "perk," for each type of Twinborn, similar to the perks of the Knights Radiant, like Shallan's ability to take Memories.

So in a way a side effect of her powers gives her the almost the same ability as a copper ferring. Hmm wonder if there is a connection or set of rule regarding mixing of powers .

Wax uses weight or mass manipulation and a form a latching .

[natc]

Shallan's effects are nothing like a copper ferring. At all. She temporarily remembers images perfectly until she draws it out onto something, after which it's about as fuzzy as your normal memories. Copper ferrings lose the memory outright until they look at it again, but if they put it back in it's gone again. It's not going to remain clear for very long either if you review it often.

Edited November 3, 2015 by natc

[killersquirrel59]

I always theorized that Iron Feruchemy involved altering the pull of gravity in a localized field rather than actually physically altering the body itself. I'm no physicist, but I figured this was mostly achieved by manipulation of the self in the Cognitive realm using the Cognitive concept of weight, which then made the physical world do backflips to match.