Without going into every calculation [I’ve showed enough work here—BTW, I did not just look this up somewhere, I calculated it then used online tools to check my work], for a .45 that weighs 2.5 pounds (an empty standard 1911 is 2.4 so I rounded), the backward force (recoil) is 8 ft-lbs. (Which is less that dropping a 1 lb weight from 3.5 m)
Not going to check your math, nor argue with your application of formulae, but consider this, the calculated muzzle energy of a .45 round is around 360ish ft/lbs. Equivalent to dropping a 360lb weight ONE foot.
Science is only science if it is applied. “Science” doesn’t tell us anything. Newton does not support the argument, when actually applied."
This is the key, call it science or math, it must be applied correctly to the situation, and even then can be correctly applied and still not explain observed results.]
Math can "prove" or disprove almost anything, depending on how it is applied. Math (according to the old story) tells us that a bumblebee cannot fly. Yet, the bee, not knowing math, flies just fine.
A saw a physics problem once, a swimmer at a pool, starts on the edge, dives in, swims to the other end, then back, and gets out right where he started. Math "proves" he went nowhere. (the exercise was to use the math and show he went nowhere) And, under math rules, it did prove he went nowhere.
Trouble is, in the real world, he did go somewhere. We saw him swim the length of the pool, and then back. distance was traveled. We observed it. But, math, applied in a certain way, says he went nowhere, since he ended up right where he started.
This is the thing about "knockdown power". It is real, it is an observed effect. You cannot deny the effect exists, people have seen it, many, many times.
However, there is, to date, no theory or formula that explains it, and none that reliably predicts it. Many have theories and ratings that appear to be correct in some situations, but do not accurately fit observed results in ALL situations. Some use energy as their main factor, some use momentum, some include bullet shape, NONE have proven accurate across the entire range of situations.
I believe none can. I believe the observed "knock down" effect is something
that happens only when shooting living animals (including people). Shooting something else does not, and cannot replicate the effect.
I believe the effect is created not by the energy or momentum, or shape of the bullet in any quantifiable way. I think it is the reaction of the body's nervous system "short circuiting" in some way, as a result of the bullet strike. it is the muscles of the animal, driven by these nerve impulses that "knock" it off its feet, when that does happen.
Because it doesn't always happen. And when it does happen, it happens in random direction and strength. Every different bullet strike contains a host of different factors, which are simply not quantifiable and so cannot be accurately used in any equation. The biggest of these is simply that every individual animal or person shot is a different individual.
There is a bell curve of results, and while the majority will be in the middle of the curve and therefore show similar results, there are situations on each end of the curve where the results are vastly different.
One guy might be "blown off his feet" by a hit from "X" and another hit with the same thing, in the same place might just stand there, or even be "blown" forward, rather than backwards. I believe the difference is due to how the target's nervous system reacted to the shot, or didn't, not because of the calculated anything about the bullet itself.
In other words, one guy might get spun around from a hit in the hand with a .45acp (and probably did, somewhere, sometime, and so the legend is born) while the next guy, shot in the hand might just look at the hole in his hand, and think, "hmm, damn, I've been shot..."
My personal theory is in my signature line, and note that its not stated in absolutes, and is based on my lifetime of observed results.