# How can you negate impact force?

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1. Sep 15, 2016

### VNV

In my science fiction universe, I have a small technology called a 'Kinetic Absorption Module'. It's not mentioned very often, but it's a key component of my supersoldiers' armor.

How it works is it acts like a shock absorber, but within a small, one inch long by one and a half inch wide diameter object that is floating in a highly viscous synthetic gelatin layer between two plates of armor. An object, such as a fist, impacts the armor, and pushes the first plate onto the KAM, and the KAM reacts by effectively cancelling the impact force. By that logic, a person in the A.T.L.A.S. Powered Combat Armor can be hit by a truck running sixty miles an hour and not move so much as an ångström, without feeling the impact force at all.

So, my question is as follows: How does one negate impact force without violating any laws of physics, killing the person in the armor, or destroying the armor?

And if we have to violate a law of physics, is there some way to make amendments to the law or laws such technology violates so as to keep the angry mob of disgruntled scientists from coming after me with proverbial pitchforks and torches?

Note: I'm unsure of how advanced such a question is, but am aware it is not rocket science, and have prefixed it as 'I'.

2. Sep 16, 2016

### Staff: Mentor

You cannot. It is impossible. Newton's third law is universal.

What you can do, however, is lessen the force by increasing the duration of the collision. This is how seatbelts, airbags, cushions, and other similar things work. A smaller force over a larger distance/time will accelerate (or decelerate) an object just as much as a larger force over a shorter amount of distance/time.

Sure. Don't give more than a cursory explanation of how the technology works and don't violate any rules you've set up in-universe for how it works. Also, if you have the technology to do something, make sure you try to think of how that technology affects all areas of society. Teleportation technology, for example, can be used for more than just transporting people over long distances. You should (generally) be able to apply it to medicine, food and commercial goods production, and a thousand other things.

I've moved this to the sci-fi fantasy writing forum, so your thread prefix has been transported into a black hole, never to return.

3. Sep 16, 2016

### Staff: Mentor

Impact forces come from changes in speed. When I drive a fast car into a brick wall, the wall exerts a very large force on the car to bring its speed down to zero. If you punch me in the chin, your fist exerts a very large force on my chin to change its speed from zero to however fast your fist is moving,

How large the force is depends on how quickly the speed change happens.

How quickly the speed change happens depends on how long of a distance it is spread over. It takes an enormous amount of force to stop a truck moving at 10 meters/sec (that's about 30 mph) in less than an angstrom because the truck has to come to a stop in less than a nanosecond. On the other hand, the brakes will gently bring the truck to stop in a hundred meters; that takes about 20 seconds, and it doesn't take so much force to reduce the speed of the truck by one-half meter per second every second

Bottom line: no, you can't do what you want without violating the laws of physics. Absorbing force is all about increasing the distance it acts over.

4. Sep 16, 2016

### VNV

I got the impression of a suit of armor with airbags in it. It make me laugh more than it should have, really.

Unfortunately, I'm not good with 'low detail', and like to have a basis of information to fall back on; know what the limits and such are for the technology. I know KAMs would be added to motor vehicles, and the material the armor is made from is used in cars, buildings, and even planetary boats. The material used to enhance the supersoldiers' bones is also used to reinforce weaker bones and replace irreparable bones.

But what about a way to essentially expand the laws of physics. The year, in my book, starts at 2320 and covers all the way up to 2700. In that timeframe, especially since it starts so late after our year in reality, isn't it possible that we would discover something to change a law written so log ago? Like, couldn't a quantum force be found that acts on objects and repels them by polarizing them or something?

And for that matter, what if KAMs did that with magnetic fields? Everything produces a magnetic field, right? So, what if they exert a polarized field that slows the incoming object down from less than an inch away by opposing their magnetic field?

5. Sep 16, 2016

### Staff: Mentor

The problem, though, is that such changes are either impossible or unknown in the real world, and even with loads and loads of time, data, and money, physicists still devote lifetimes to figuring out new laws of nature. So if you change something in your book, there's essentially have no way of verifying whether or not it's even possible.

If the magnets exert a force on an object, the object exerts a force on the magnets, and by extension whatever the objects are mounted to. Also, no, not everything produces a macroscopic magnetic field that can be used. Most objects would react only weakly with even very strong magnetic fields.

6. Sep 16, 2016

### VNV

What about organic beings? Do we, humans and bears and such, produce a macroscopic MF?

7. Sep 16, 2016

### billy_joule

Why not do your own experiment?
Go to your kitchen and see if a fridge magnet sticks to you.

Water is diamagnetic so water based beings can be made to levitate with very (very very) strong magnets;
http://www.ru.nl/hfml/research/levitation/diamagnetic/

8. Sep 16, 2016

### VNV

I'm aware that there are differences in magnetic fields. If magnets stuck to me, I wouldn't keep dropping them on my toes.

The link is rather interesting, thank you for it. I actually didn't know water was diamagnetic; or that diamagnetism was a thing at all. I've only begun genuinely looking into such things, mostly because this has sparked enough that some cogs have begun turning.

9. Sep 16, 2016

### DrStupid

The hypothetical "Kinetic Absorption Module" needs to bypass the force to something else, e.g. into the ground. You don't need to explain in detail how that works but it could be a good idea to mention that the KAM needs something to interact with. It wouldn't work in free space and using it in a china shop could result in a big pile of shards.

10. Sep 16, 2016

### BillTre

I see a few ways you can do this, some already mentioned.
1) Slow dissipation of the force from slow deceleration. This would still result in movement of the impactee. Does not meet your criteria.
2) Highly efficient redirection of the force around the impactee. Something like your capsule shoots out sideways, but also somewhat backwards taking the force with it. Probably would still result in the impactee moving. The armor could get used up.
3) A rigid suit with a force generator on the opposite side of the impact. Force going back equals force going forward. Suit has to be rigid to keep from crushing the impactee by the Crusher (gratuitous Star Trek reference).

and finally if you want to get out there SciFi-wise (meaning not currently realistic):
4) The capsule takes the impact force and transfers it an alternative version of the multiverse (mechanism unknown). The force leaves our universe and therefore has no effect on the impactee. Maybe conservation would require it to come back somewhere however. Or at a different time.
5) Perhaps the capsule could store the impact in some kind of circular flow of energy within its structure (highly curved space the force can enter, but only leave slowly or maybe the mechanical equivalent of the effect of a lens on light bending the direction of the force), releasing it slowly later. Somewhat like an airbag, direction release might be a problem. Might still get movement.
6) The force is converted into dark energy or matter.

11. Sep 16, 2016

### jackwhirl

These two are your best bet.
The first would be like Halo's armor lock.
The second is what Ironman should use his boosters for, rather than just getting knocked around. Stark should be like a scrambled egg inside his armor.

One more option that is quite out there would be to borrow the mechanism of Superman's infinite mass punch.
Use relativistic mass to temporarily boost your inertia. This would cause the velocity portion of your momentum response to be very small.

12. Sep 16, 2016

### DrStupid

That requires the energy equivalent of the relativistic mass increase. This energy must come from somewhere and the energy transfer must be symmetric in order to avoid a resulting net force which could be even worse than the punch to be defeated. With these restrictions it could work in theory.

13. Sep 16, 2016

### jackwhirl

Neat. Since I'm way way outside my field here, would that energy equivalent happen to follow e=sqrt((mc^2)^2+(pc)^2)?

14. Sep 16, 2016

### DrStupid

In principle yes, but it would be a good idea to keep the total momentum constant and that means for v<<c that the energy equivalent is in fact dE=dmc².

15. Sep 16, 2016

### jackwhirl

Got it. A few more questions: If we were to annihilate a proton/antiproton pair, do we get the mass energy equivalent of both masses? Second, to create a relativistic mass of 50 tons, would were need 25 tons each of protons/antiprotons?

16. Sep 16, 2016

### Staff: Mentor

In the first case, you get a shower of particles and radiation whose kinetic energy and masses are equal to the sum of the proton and antiproton's masses plus any kinetic energy they had upon impact. Your understanding of the 2nd case is pretty much correct.

17. Sep 16, 2016

### jackwhirl

Ok. So, to sum up for @VNV, ignore the relativistic mass angle. It would require a pocket universe with a star + Dyson swarm or a kugelblitz or something equally ridiculously impractical.
It would be far less expensive to just make the armor weigh 50 tons.
Also, Superman cheats. :(

18. Sep 28, 2016

### VNV

Thank you all for your help. I didn't quite understand all of it when you got really scientific with it(like adding two d's to e=mc squared), but I got the general idea of it.

Force must either be equalized or it has to go someplace else.

Thank you all for your time.