El Mahdi
Muad'Dib of the Anauroch
Penetration isn't everything.
There are several different things that all contribute to how damaging a weapon is to the body - penetration, energy transfer, momentum transfer, how quickly and well the resulting wound stops bleeding, and so on.
Aren't "momentum" and "energy" the same. Essentially it's just kinetic energy, isn't it?
Energy is never in Newtons. Newtons are a unit of force, not energy.
Your are correct. I mispoke. I believe we were talking about how hard an arrow hits, and it was said that a longbow arrow would be equivalent to high caliber bullets. That's simply not true. Not even close.
He talked about how "hard" it hit. We could debate what that really means, but I think for most intents and purposes, how "hard" a hit is isn't about energy, it is about momentum transfer. And on that score, the arrow and the bullet are on more even terms. The bullet is faster, but you aren't squaring velocity, and the arrow is much heavier than the bullet.
Plus, arrows almost never pass all the way through the target, while bullets sometimes do.
The last part of that isn't true. I've seen arrows go clean through a deer. It's not super common, but it definitely happens enough to not be in the "almost never" category. It happens a lot more than you may think. And those are simply modern coumpound bows*. Even a modern compound bow doesn't have the impact of a 200 lb. pull longbow with a heavy war arrow. Even the most powerful compound bows only have pulls in the low to mid 100's. It's because of the geometry of the arrow head. That's why if you took a hollow point round and a steel jacketed round of the exact same caliber, weight, and load - the steel jacketed round would cut through like butter while the hollow point round would expand and not penetrate as easy (however, it will transfer more energy to the surrounding tissue).
How hard it hits is about energy. Or more specifically, about the energy of the projectile, the weight of the projectile, and the shape of the projectile. (So it is about energy, just not only about energy.)
*For those who don't know, and because this subject always seems to wander in this direction...
Compound Bows are no more powerful than a similiar strength short bow, long bow, or if you want - a recurve bow.
A 100 lb. pull compound bow would have virtually the same force as a 100 lb. pull recurve bow. The only real difference is a compound bow is easier to hold a draw than a recurve bow. A 100 lb. pull recurve bow means you would be holding 100 lbs. with it drawn. A 100 lb. pull compound bow would only take about 75 lbs. to hold (however, you would initially still pull the entire 100 lbs.).