# How does or doesn't the physics of Mistborn mesh with Newtonian physics?

In the Mistborn series by Brandon Sanderson, it is mentioned a few times that if you push some thing that's lighter than you, it will be pushed away, while if you try to push something heavier than you, you will be pushed away.

The problem starts when you learn about explotions: when you throw a coin out of your hand at a very high speed, you will be thrown back. For Mistborns this is not a problem - they burn pewter in order to stay balanced. But how do steel burners stay balanced when they throw coins?

I have read just the first three books, so please: no spoilers!

What Kelsier describes as "pushing with your own weight" could also be seen as a primitive understanding of inertia: heavier objects are harder to accelerate (or decelerate) than lighter ones. If you step on a skateboard (to reduce friction) and throw a basketball away from you, you will be pushed back by the force of your throw (Newton's 3rd law states that while you push on the ball, it pushes on you with equal force), but you will go much slower since you are much heavier.

This is, at least to me, exactly what happens in Scadrial : as a coinshot's body is much heavier than the coin, the reciprocal force (assuming allomancy doesn't violate Newton's 3rd law) will only have a small effect on the user's body. As such, the coin gets shot real fast while the coinshot only suffers a little recoil.

Also, in the books, Vin often attempts to push objects using all her allomantic might, even using duralumin to enhance her push (thus exerting more force). At these times, she is often described as bracing herself on heavy metallic objects (or metallic objects fixed in a solid structure) to maintain balance (i.e. not being thrown off by the reciprocal force). As a full Mistborn, Vin also uses pewter to enhance her body's capacity to endure crushing pressure to exert even more force while pushing objects.

In most cases, I believe that a physically fit coinshot could throw coins out at deadly speed (from his center of mass, not his hands) while only suffering light recoil, which his body should be able to absorb. And as long as his body could resist the strain and the pressure, he could brace himself on structures behind him to push coins even faster.

But how do steel burners stay balanced when they throw coins?

Presumably they have to brace for it, the same way someone who's experienced at shooting guns knows how to deal with recoil (a very similar situation, concerning the speed and weight of the projectiles).

A coinshot (steel pusher) can use their power to push against an object behind them for bracing while they are firing off coins ahead of them.

• Hello ! Where does this information come from ? Can you add a quote or at least say when it is mentioned ? Commented Jul 18, 2013 at 14:16
• @Kalissar: It's a technique used very often by the protagonists of both the trilogy and Allow of Law, if I recall correctly. Pick a fight scene, it'll probably turn up. Commented Jul 18, 2013 at 22:29