Superhuman archery material sciences

[TeChameleon]

The character as designed (at least for the moment, it's kinda subject to change) follows a denser build-type than the standard superhero (think the comic-book verson of Fantastic Four's Thing as opposed to Superman), but isn't supposed to be overwhelmingly heavier than somebody of that build would be.

That being said, from what I remember of the physics of archery, the recoil question is... odd. It's been a long time since I did anything with a bow and arrow, but what dim memories I retain suggest that the bow is more likely to jump out of your hand forwards if you're not holding onto it properly.

And, well, unless something changes drastically, the character is going to have at least some government connections, so arrows with more esoteric components are at least somewhat plausible.

Oh, and he's primarily going to be up against other super-types or ultratech opponents, so overpenetration is less of a worry- fairly rare for him to be going up against soft targets.

[factotum]

While there is a force exerted back on the archer, it's both mitigated via the string plus the overall force distribution is unequal (the arrow is going forwards after all), so the archer isn't seeing the same force as the arrow is getting.

Well, yes they *are* seeing the same force the arrow is getting, that's the entire point of Newton's Third Law--you don't get to bypass it because you're releasing the power in a spring rather than pushing it yourself. The string exerts a force on the arrow to accelerate it, that force is transmitted through the string to the arms of the bow, and from thence to the hand of the archer. The only mitigating factor I can think of is that the bow limbs are being flung *forward* as the spring tension is released, which will be adding a forward force to the equation and thus reducing the recoil somewhat.

In the normal course of events the recoil on a bow isn't going to be anywhere near what it is from a gun because the arrow is much slower than a bullet, but we're explicitly talking about a super-powered individual wielding a super-bow here, so I think the recoil may well be significant.

[Brother Oni]

That being said, from what I remember of the physics of archery, the recoil question is... odd. It's been a long time since I did anything with a bow and arrow, but what dim memories I retain suggest that the bow is more likely to jump out of your hand forwards if you're not holding onto it properly.

Yep, this is correct - it's why Olympic recurves have weights on poles, to both dampen the recoil and to stop the bow literally jumping out of your hand when you loose.

In kyudo, they compensate instead by letting the bow 'spin' in the hand, to bleed off this excess energy.

Well, yes they *are* seeing the same force the arrow is getting, that's the entire point of Newton's Third Law--you don't get to bypass it because you're releasing the power in a spring rather than pushing it yourself. The string exerts a force on the arrow to accelerate it, that force is transmitted through the string to the arms of the bow, and from thence to the hand of the archer. The only mitigating factor I can think of is that the bow limbs are being flung *forward* as the spring tension is released, which will be adding a forward force to the equation and thus reducing the recoil somewhat.

Tod from Tod's Workshop test fires a 1250lb draw weight crossbow in this video: link.

Assuming a typical 30% efficiency for metal prod crossbows, that's 375lbs of force being exerted on the bolt or ~1.7kN, which means that force is being transmitted back into him.

That's about half a full power strike from a heavyweight boxer, or about a jab / moderately hard shove - there certainly doesn't seem to be that level of recoil when Tod shoots the crossbow.

I'm not saying that you're wrong - my level of physics understanding agrees with you. However my practical experience says it's not as simple as a direct application of Newton's Third Law.

[factotum]

Tod from Tod's Workshop test fires a 1250lb draw weight crossbow in this video: link.

Assuming a typical 30% efficiency for metal prod crossbows, that's 375lbs of force being exerted on the bolt or ~1.7kN, which means that force is being transmitted back into him.

I think the way it works is this: the force of the drawn string will act on the bolt and will accelerate it over the few inches of travel of the string. The recoil force that acts on the rest of the crossbow will be derived from the forward acceleration of the bolt (via F=ma), but the thing is, the crossbow (plus the person holding it) is much, much heavier than the bolt is, so they don't get as big of a kick.

The suspension on your car relies on the same principle--when you go over a bump the force exerted on the bottom of the suspension spring is pretty much the same as the top end of the spring exerts on the car; what causes the bump to be less severe for the occupants of the car than it is for the wheel is because of the difference in weight between the wheel assembly and that of the car. This is why bigger, heavier cars will generally have a smoother, more comfortable ride than a small, light one.

[Knaight]

The forces are different - you can abstract this down to basically a point diagram just fine, black box style, where Newton's laws do state that the force of the arrow released is opposed (here mostly on the archer, though there's moving air and the like), as is the force of the arrow on impact (here mostly on the target, though again, there are surroundings). The forces on each end do not need to be the same though; which in this case tends to come across in the drastically different accelerations involved.

It's in an impulse/momentum framework where you start seeing larger scale conservation. Momentum is conserved through the entire system, with the change in momentum from shooter and target being the same in a vacuum. Momentum transfer is connected to force via impulse (change in momentum), which is the integral of Fdt over the duration of an impact.