But is it really the sudden stop?

[RyanW]

At least some fall damage is due to sudden deceleration, but some of it is also the fact that the bits that hit the ground stop while the bits above them try to keep going.

If, by magic or technology, you could stop a fall instantly by stopping every part of a person simultaneously, how much would that reduce fall damage?

[sir_pudding]

That would use the rules for Acceleration rather than Collisions. Assuming a spread eagled fall at 60 yards per second you would need to make a HT-2 roll (-4 for 6G; +2 for position) and lose 1 FP per margin of failure and black out on a critical failure (although in this case you would actually red out).

[acrosome]

Well, if you sort of magically remove all kinetic energy from every individual molecule at the moment of impact then theoretically you would take no damage whatsoever.

Except that you'd also be frozen solid.

And then shatter from thermal shock.

Very messy.

[Armin]

But what if you didn't remove all kinetic energy; just that along the falling vector. I think that's what RyanW is actually asking about.

There shouldn't be any freezing, then. And you shouldn't red or black out, because all your blood is still doing exactly what it ought to, right? And there's no brain smashing against skull, no other internal collisions or malformations. Are there really any issues if you could magically catch someone like that?

[sir_pudding]

Originally Posted by Armin

But what if you didn't remove all kinetic energy; just that along the falling vector. I think that's what RyanW is actually asking about.

There shouldn't be any freezing, then. And you shouldn't red or black out, because all your blood is still doing exactly what it ought to, right? And there's no brain smashing against skull, no other internal collisions or malformations. Are there really any issues if you could magically catch someone like that?

No, because there would be no difference between that and just teleporting to the ground.

I don't think that the OP meant that though.

[malloyd]

Originally Posted by Armin

But what if you didn't remove all kinetic energy; just that along the falling vector. I think that's what RyanW is actually asking about.

Where does that energy *go*? Ultimately what inflicts the damage is some of the energy of the fall gets dissipated inside your body moving and tearing stuff. If the energy outright vanishes, clearly it isn't going to be doing anything to your body.

Of course you are violating two rather fundamental physical laws (conservation of energy and relativity (because slowing everything down at once is equivalent to infinite rigidity, and hence an infinite speed of sound)) to do it, so who knows, maybe the Hounds of Tindalos come out and rip you to bits before you can activate the effect to prevent the universe from terminating.

[Anthony]

Originally Posted by malloyd

Of course you are violating two rather fundamental physical laws (conservation of energy and relativity (because slowing everything down at once is equivalent to infinite rigidity, and hence an infinite speed of sound)) to do it, so who knows, maybe the Hounds of Tindalos come out and rip you to bits before you can activate the effect to prevent the universe from terminating.

You can, of course, do it in a non-instant manner with known effects -- gravity accelerates all parts of an object simultaneously.

[whswhs]

Originally Posted by malloyd

Of course you are violating two rather fundamental physical laws (conservation of energy and relativity (because slowing everything down at once is equivalent to infinite rigidity, and hence an infinite speed of sound)) to do it, so who knows, maybe the Hounds of Tindalos come out and rip you to bits before you can activate the effect to prevent the universe from terminating.

I don't think the latter is necessarily the case. If you activate a body force field, rather than a surface force field, it will act on the entire mass of the body at once, whether the body is infinitely rigid or made of gelatin. Well, you could quibble about the force having a finite velocity of propagation, but that velocity could be c or close to it, and much faster than the speed with which a mechanical impact propagates into the interior.

[Anthony]

Originally Posted by RyanW

If, by magic or technology, you could stop a fall instantly by stopping every part of a person simultaneously, how much would that reduce fall damage?

To zero. The damage is all from different parts of the body decelerating at different rates.

[Flyndaran]

From falling you almost always hit with some body part first which takes the most damage. Hitting everywhere instantly would change the impact to full body.
I think this would result in the common gaming aspect of generic Hit Point loss.