Coinshots And Guns

[Sirscott13 he/him]

Why can't a coinshot stop bullets with a powerful push. Understanding the physics as best I can a bullet has roughly 300N of force but an average male should have a a weight force of roughly 900N.

Correct me if my math is wrong but shouldn't a coinshot be immune to gunfire by this principle?

[king of nowhere]

the bullet moves too fast to see, therefore the coinshot doesn't have the time to react and push it. he only can if he's prepared in advance and has good timing. It's like grabbing arrows midflight, really. it can be done, but it requires incredible reflexes. just because humans have hands they are not immune to arrows.

[Kaymyth she/her]

If they're ready for the shot, maybe.  But were I a Coinshot, I'd go Pushing the guns out of peoples' hands before the shooting started.

 

Now, a steel Compounder, they'd be able to do impressive things with Pushing bullets and catching arrows/crossbow bolts.

[Oudeis he/him]

The other thing to note is that steelpushes don't provide infinite force. A bullet comes at you with 300N. You're able to apply 100N of force to that bullet via steelpush; you cannot simply push to infinity the way you cannot simply lift an elephant by flexing your muscles to infinity. The bullet is still coming at you with 200N of force, enough to harm you.

 

The other thing to note is that it's not unheard of for someone to fire bullets faster than one by one. Push on three bullets and a pretty big dude has now matched his own weight and on the fourth bullet, you're now flying backwards at ... what, 75N? Is my math right?

[Moogle]

As an alternative model for Allomancy, there's this thread.

 

Under this model, Allomancers don't directly exert however many N of force, they input kinetic energy into the system. A bullet has a lot of kinetic energy, and an Allomancer has a limited amount of power.

 

Also, I'm not sure your measurement of a bullet having 300 N of force makes sense. It's a weird measurement. The obvious ways to measure a bullet would be speed (500 m/s is a figure I've seen) and momentum/impulse. Maybe you meant 300N-s?

Edited February 20, 2015 by Moogle

[Dunkum he/him]

Moogle, on 19 Feb 2015 - 11:29 PM, said:

Also, I'm not sure your measurement of a bullet having 300 N of force makes sense. It's a weird measurement. The obvious ways to measure a bullet would be speed (500 m/s is a figure I've seen) and momentum/impulse. Maybe you meant 300N-s?

I was going to say something along these lines. It doesn't make a whole lot of sense to talk about a bullet having force. a force was applied to the bullet, but after it has been shot, the only forces acting on it are air resistance and gravity, and neither of those is propelling it forward (unless it was shot directly down, I guess), I suppose it will cause a force to act on the target, but to say it has a force doesnt really sound right. Momentum, speed, acceleration and mass are the important figures. A little back of the envelope calculation (with a lot of rounding) using the numbers for a Colt .45 suggests that for a shooter within 30 ft (about 10 meters) you would need to generate something like 2100N of force to slow the bullet enough to stop it, which seems a bit high for your average coinshot. you could slow it down enough to reduce injury with less force, but the other limiting factor here is time. You have to react within a tenth (closer to one hundredth, in fact) of a second. And, if you are reacting to the sound of the gunshot, you have even less time, since sound doesn't travel that much faster than a bullet (a difference of about 60 m/s), so in the time it takes the sound to reach you, the bullet is only a little bit behind (for 10 m, that means the bullet is about 1/200th of a second away).

[Kaymyth she/her]

It does my dear little nerdy heart good to see all this math.     

 

But...I think the major point that a lot of people are missing is that you don't have to stop the bullet, just deflect it.  So you don't have to completely counteract the force/momentum of the bullet, you just have to give it enough of a nudge that it goes flying off in another direction.  That's a whole lot easier.

[Ashiok]

But that implies that it's not flying straight at the bit where all the allomatic lines are coming from. Also, in pushing against it, you'd take the force of the bullet, distributed along your entire body, no? I imagine that wouldn't feel too good.

[Kaymyth she/her]

But that implies that it's not flying straight at the bit where all the allomatic lines are coming from. Also, in pushing against it, you'd take the force of the bullet, distributed along your entire body, no? I imagine that wouldn't feel too good.

 

Hm.  Angle would be an issue.  Any object is going to follow the path of least resistance, though, so even a small variation off from your center of gravity may be enough to deflect it.

 

And again, deflecting isn't taking the full force of the bullet, just a fraction's worth to move it off in another direction.

 

It still doesn't solve the problem of speed and reflexes, mind.  I still think that a steel Compounding Twinborn is going to have a lot more success at this sort of thing than a normal Coinshot (and even then, it's going to be a far from perfect score).  If Pushing bullets shot at you were easy, Wax wouldn't have seven old gunshot wounds.

[Dunkum he/him]

Kaymyth, on 20 Feb 2015 - 2:11 PM, said:

Hm. Angle would be an issue. Any object is going to follow the path of least resistance, though, so even a small variation off from your center of gravity may be enough to deflect it.

And again, deflecting isn't taking the full force of the bullet, just a fraction's worth to move it off in another direction.

It still doesn't solve the problem of speed and reflexes, mind. I still think that a steel Compounding Twinborn is going to have a lot more success at this sort of thing than a normal Coinshot (and even then, it's going to be a far from perfect score). If Pushing bullets shot at you were easy, Wax wouldn't have seven old gunshot wounds.

Yea, I think the speed is the real problem, especially if you are reacting to the sound of the gunshot. You have a fraction of a second to react, and part of that is spent just in the neurological processes so I think you need steel/zinc in order to have the mental capacity to react in time. As someone mentioned upthread, you have a far better chance to avoid the bullet by pushing on the gun before they pull the trigger than you do by actually deflecting the bullet.

[Kaymyth she/her]

Yea, I think the speed is the real problem, especially if you are reacting to the sound of the gunshot. You have a fraction of a second to react, and part of that is spent just in the neurological processes so I think you need steel/zinc in order to have the mental capacity to react in time. As someone mentioned upthread, you have a far better chance to avoid the bullet by pushing on the gun before they pull the trigger than you do by actually deflecting the bullet.

 

And if you're reacting to the sound, you're doubly in trouble, because most bullets travel faster than the speed of sound.

[Bort he/him]

There is a line in Alloy of Law (I think in the ballroom where Steris is kidnapped) where Wax has a thought about how he can only deflect bullets if he is ready for them.

[Moogle]

But that implies that it's not flying straight at the bit where all the allomatic lines are coming from. Also, in pushing against it, you'd take the force of the bullet, distributed along your entire body, no? I imagine that wouldn't feel too good.

Not necessarily! Conservation of force does not seem to exist in Allomancy. Vin only starts rising when she's pushing on a coin stuck on the ground. If conservation of force was a thing, she should start rising immediately when she drops a coin midair.

Previous post has a link on this!

[Oudeis he/him]

Also, I'm not sure your measurement of a bullet having 300 N of force makes sense. It's a weird measurement. The obvious ways to measure a bullet would be speed (500 m/s is a figure I've seen) and momentum/impulse. Maybe you meant 300N-s?

 

 

I was going to say something along these lines. It doesn't make a whole lot of sense to talk about a bullet having force.

 

...

 

Momentum, speed, acceleration and mass are the important figures.

 

Force is mass times acceleration; since a bullet has both mass and velocity, it has force. I guess in a weird sorta way no thing every has force, forces just exist in the world a function of other things, but you're being preposterously pedantic right now. The meaning was clear, and pointing out that "technically" isn't doing anything useful. When a bullet hits a human body, force will be applied to the body and to the bullet. If you attempt to change the trajectory of a moving bullet, you must apply force. Arguing about where the force "actually" is serves no real purpose.

 

A few other notes:

 

if you can see steellines, you prolly aren't relying on sound to know when bits of pushable metal are suddenly flying at you. If you're not burning steel, then yes, it's definitely too late to deflect.

 

Yes, there will likely be a slight angle between the trajectory of the bullet and your center of mass, but you have a very short window, and applying enough force at an angle that steep to make the bullet actually miss you is less easy than people are making it seem. If they're smart enough to aim roughly below your core, you could easily have to push the bullet two feet or more off target before it's not heading right for one of your favorite internal organs. You'd be much, much more effective at Pushing enough to deflect bullets being fired at your buddy.

 

Just for those of you keeping score at home; let's be careful not to conflate modern bullets with examples from Wax. Between Wax's current time and our modern day guns, force (yes, I'm using the term force here) changes drastically. I recognize that no one has yet gotten chocolate in their peanut butter, but I see both chocolate and peanut butter at play, and I wanna make sure everyone knows what everyone's talking about.

 

EDIT:

 

Conservation of force does not seem to exist in Allomancy. Vin only starts rising when she's pushing on a coin stuck on the ground. If conservation of force was a thing, she should start rising immediately when she drops a coin midair.

 

I read the thread and I don't see where you're getting this from. Vin should not shoot upwards when she pushes down on a coin, any more than I should be able to fly by flapping my arms. Yes, I'm pushing air molecules down. That same force is being applied to force my body upwards, but it's nowhere near enough to fight gravity. Vin Pushes downwards on the coin, and force is applied to her body giving her an upwards vector. It's not enough to make her rise, but that doesn't mean it doesn't exist.

Edited February 20, 2015 by Oudeis

[Sirscott13 he/him]

Would not someone like wax using a steel bubble to push in all directions be more effective at stopping bullets without a reaction time? Also he could tap weight to apply greater "force" on all his pushes.

[Blaze1616 he/him]

I could have sworn that Wax actually mentions this in the book. How he can't deflect, but he can alter the path of the bullet, so when he creates a pushing "bubble" around him he's merely hoping to send bullets on slightly altered paths, hopefully missing him and/or his vital organs. I could have sworn it is in the book.

[Dunkum he/him]

Would not someone like wax using a steel bubble to push in all directions be more effective at stopping bullets without a reaction time? Also he could tap weight to apply greater "force" on all his pushes.

Yea, Wax's steel bubble thing would help, but if memory serves, he mentions in the book that it is a difficult trick, and most people can't/don't know how to do it.

if you can see steellines, you prolly aren't relying on sound to know when bits of pushable metal are suddenly flying at you. If you're not burning steel, then yes, it's definitely too late to deflect.

Good point, that should have occurred to me; but that still leaves you with something like .01 seconds for every 10 feet away the shooter is (i.e. .03 for 30 feet, .1 for 100 ft, etc. this is an approximation, again based on the numbers I found for a colt .45, some guns will likely be faster)

and you are right about my nitpicking, but saying the bullet "has x N of force" just sounds really really weird to me.

[Moogle]

I read the thread and I don't see where you're getting this from. Vin should not shoot upwards when she pushes down on a coin, any more than I should be able to fly by flapping my arms. Yes, I'm pushing air molecules down. That same force is being applied to force my body upwards, but it's nowhere near enough to fight gravity. Vin Pushes downwards on the coin, and force is applied to her body giving her an upwards vector. It's not enough to make her rise, but that doesn't mean it doesn't exist.

 

When I say "conservation of force", I mean in the sense that people here were saying "oh if you have to Push on a bullet, you're going to experience a huge force pushing you away!". When Vin Pushes on a small object, despite giving it a serious amount of force, she does not experience the same force in reverse (unless it's anchored). I was simply saying that someone Pushing on a bullet coming at them is unlikely to experience much force thanks to the massive difference in weights.

 

Force is mass times acceleration; since a bullet has both mass and velocity, it has force. I guess in a weird sorta way no thing every has force, forces just exist in the world a function of other things, but you're being preposterously pedantic right now. The meaning was clear, and pointing out that "technically" isn't doing anything useful. When a bullet hits a human body, force will be applied to the body and to the bullet. If you attempt to change the trajectory of a moving bullet, you must apply force. Arguing about where the force "actually" is serves no real purpose.

 

Entirely off-topic at this point:

I'm not trying to argue about where the force actually is, I'm saying using Newtons is using the wrong unit. Saying a bullet has "300N" of force gives us no reference frame for how hard a Push would be required to stop a bullet. Force is dependent on time. If I get hit by a 100N force for 0.00001 seconds, it's not going to do much to me (well, in a theoretical sense, I suppose it could blow a hole through me if the force was confined to a relativity small area). How long is this 300N from a bullet being exerted on me? On the bullet? For how long do I need to exert a 300N force on the bullet in the opposite direction to stop it? For 0.1 seconds? 1 second? It's impossible to know from the figure given because it's the wrong unit.

 

The bullet's velocity/momentum/kinetic energy would all be acceptable measures of the bullet, but force makes little sense. I can't use this 300N figure to do any Pushing calculations. I can't move at 75N, though I could have 75N applied to me for a duration of however many seconds. I could move at 1m/s, or have 300J of kinetic energy. If bullets exert a force of 300N on impact, this is useful information, but only for designing materials meant to resist bullets, not for Coinshots. Imagine someone told you they could move at 5 pounds per hour. It just doesn't make sense. Pounds per hour are not a measure of speed.

 

Slightly pedantic, sure, but it was just meant as a simple physics note at the time.

Edited February 20, 2015 by Moogle

[Voidus]

Force is mass times acceleration; since a bullet has both mass and velocity, it has force. I guess in a weird sorta way no thing every has force, forces just exist in the world a function of other things, but you're being preposterously pedantic right now. The meaning was clear, and pointing out that "technically" isn't doing anything useful. When a bullet hits a human body, force will be applied to the body and to the bullet. If you attempt to change the trajectory of a moving bullet, you must apply force. Arguing about where the force "actually" is serves no real purpose.

Velocity is not the same as acceleration, bullets in flight don't have force, they exert a force when they collide with something but so does the thing the collide with. 300N is just not a good way to describe a bullets motion or difficulty in stopping.

I don't believe it's preposterously pedantic, 300N is a completely meaningless and misleading figure.

[ThirdGen]

I could have sworn that Wax actually mentions this in the book. How he can't deflect, but he can alter the path of the bullet, so when he creates a pushing "bubble" around him he's merely hoping to send bullets on slightly altered paths, hopefully missing him and/or his vital organs. I could have sworn it is in the book.

 

Yes, something like this.

[king of nowhere]

Not necessarily! Conservation of force does not seem to exist in Allomancy. Vin only starts rising when she's pushing on a coin stuck on the ground. If conservation of force was a thing, she should start rising immediately when she drops a coin midair.

Previous post has a link on this!

Actually, I believe the real thing is that steelpush has a finite velocity. it doesn't apply a force on the metal like a magnet would do. it is instead like pressing an ethereal thumb on the metal to push on it. Proof: vin steelpushes coins with duraluminium, and they don't take fire. they also fail to go past the sound barrier. this shows that there is only a finite amount of speed you can impart to an object with a steelpush. if the object is light, it will reach that speed and then stop accelerating, even if you push stronger. and that's why vin wasn't getting enough push on the coin to lift herself, before the coin was on the ground.

[natc]

Velocity is not the same as acceleration, bullets in flight don't have force, they exert a force when they collide with something but so does the thing the collide with. 300N is just not a good way to describe a bullets motion or difficulty in stopping.

I don't believe it's preposterously pedantic, 300N is a completely meaningless and misleading figure.

That.

Doesn't matter how fast the bullet is, aside from air resistance and the reaction force of air resistance if the bullet is not speeding up or slowing down (or causes something to do so) it is experiencing 0N and exerting 0N. When fired and on impact you can measure it, but in midflight only air resistance and gravity would matter, so it's rather pointless to discuss a bullet after being fired in terms of Newtons.

If you fire the gun in space it will have nearly 0N being applied to it yet maintain supersonic speeds until it hits a stray planet or gets caught in a gravitational field. While also moving directly away from the center of the universe near the speed of light (I think? I forget) because that's roughly how fast it was moving relative to that spot before it was even fired, like everything else in existence. Only the change in velocity matters for force, as velocity itself is relative with no absolute zero.

Edited February 22, 2015 by natc

[Ashiok]

When I say "conservation of force", I mean in the sense that people here were saying "oh if you have to Push on a bullet, you're going to experience a huge force pushing you away!". When Vin Pushes on a small object, despite giving it a serious amount of force, she does not experience the same force in reverse (unless it's anchored). I was simply saying that someone Pushing on a bullet coming at them is unlikely to experience much force thanks to the massive difference in weights.

Well, when Vin Pushes on an object, it's like there's a thing exerting force on the object from her, no? Let's say that the blue lines transfer the force, just for a visual. When Vin pushes a coin down, the only thingy (totally the technical term) acting against her push is air resistance (until it hits the ground). When a bullet is pushed against, there's the added thingy (velocity) from the bullet that makes it even harder to push against, therefore possibly throwing someone back (or at least off balance).

I dunno, I'm not really a physics person, nor have I kept up on Cosmere theories. This is just my two clips on the subject. Take it as you will.

[natc]

Well, when Vin Pushes on an object, it's like there's a thing exerting force on the object from her, no? Let's say that the blue lines transfer the force, just for a visual. When Vin pushes a coin down, the only thingy (totally the technical term) acting against her push is air resistance (until it hits the ground). When a bullet is pushed against, there's the added thingy (velocity) from the bullet that makes it even harder to push against, therefore possibly throwing someone back (or at least off balance).

I dunno, I'm not really a physics person, nor have I kept up on Cosmere theories. This is just my two clips on the subject. Take it as you will.

Not deep into physics myself, but when you apply force to something you experience the same amount of force in the other direction pushing back. Hence why jet propulsion works and gravity doesn't pull you through the floor.

So theoretically as soon as you push the coin, if it works normally you should be getting pushed up, well a teensy bit at least. Though with how heavy you are I doubt you'd get far until the coin hits something and gets anchored in place. Pushing a whole mass of coins forward should definitely throw you backward more noticeably than vertical pushing though. Firing a shotgun while seated should tell you that much, and that's just a short burst at the moment of firing and not a continuous push. I swear NASA recommends handguns as survival equipment in space just for propulsion purposes.

Either we're ignoring Newtonian motion, or the allomancy isn't generating force in the first place.

Edited February 22, 2015 by natc