# Kinetic magical boxers - consequences [closed]

I have little problem with physics and I do not know how to formulate question to get help of a google.

Say, in my settings I have a Boxers (and other street martial artists) which can store impact energy (Charge it by hitting something in charging mode - the hit in charging mode will not cause any damage at all, energy is sucked inside). If fully charged boxer can release instantaneously 5000J of energy into opponent jaw, what is gonna happen? If the opponent's can be sent flying by the hit, would attacker's wrist remain intact? I am sorry I do not have strong grasp on physics. All newton laws during impact applicable. I am going to give here some universal numbers if someone would like to do mathematical explanation:

Input data

Hero's weight: 70kg

Hero's unmodified punch: 500J

Weapons's released energy: 5000J

Enemy's weight: 100kg

Questions

What is gonna happen with both participants?

What is gonna happen with Hero if he hits solid wall from stone?

• "boxers and other street weapons" does not make sense. According to wiktionary, "boxer" could be a person who boxes (either the sport, or as in packaging), a type of dog, a type of car engine, or a type of underwear. None of these are what I would consider "street weapons" (the dog might be a stretch). Did you mean boxing gloves? Or do the people themselves have this ability, which can also be infused into inanimate objects? (Or did you mean "other street fighters"?) – Matthew May 12 '20 at 14:18
• To answer some of your questions, we need to know if this magic violates Newton's Third. It will make a huge difference if "charging" results in a "reaction" force equal to the (non-existent) action force and no reaction during "release". – Matthew May 12 '20 at 14:23

According to Wikipedia's article on muzzle energy:

A 180-grain (12 g) bullet fired from .357 magnum handgun can achieve a muzzle energy of 580 foot-pounds force (790 J). A 110-grain (7.1 g) bullet fired from the same gun might only achieve 400 foot-pounds force (540 J) of muzzle energy, depending upon the manufacture of the cartridge. Some .45 Colt ammunition can produce 1,200 foot-pounds force (1,600 J) of muzzle energy, far in excess of the average listed above.

(...)

Some jurisdictions stipulate minimum muzzle energies for hunting. For example, in Denmark rifle ammunition used for hunting the largest types of game there such as red deer must have a kinetic energy E100 (i.e.: at 100m range) of at least 2700 J and a bullet mass of at least 9 g or alternatively an E100 of at least 2000 J and a bullet mass of at least 10 g. Namibia specifies three levels of minimum muzzle energy for hunting, 1350 J for game such as springbok, 2700 J for game such as hartebeest and 5400 J for big game, together with a minimum caliber of 7 mm.

I couldn't find data for shotguns on Wikipedia, but I found some mentions in other sites of a 12-gauge delivering up to 4,453 joules on a shot.

So your magical puncher is basically delivering a shotgun shot at point blank to someone else's face. This can break all facial bones and deform the victim's head so much that their own mother would have a hard time ID'ing them in the morgue.

If the magic does not protect the puncher, their hand also suffer the same damage they would take from a shot. Also their arm muscles might rip from the high speed of the punch.

Hitting a concrete wall would be like shooting a wall with the muzzle touching it. DON'T DO THIS IN REAL LIFE. The shrapnel bouncing back may kill you. In the case of the magic puncher, their hand bones would be the shrapnel.

What is gonna happen with both participants?

They're in for a world of hurt. Punches are generally measured in units of force and joules are a unit of energy, but let's assume that Hero can punch like an average boxer. One study found that the average punching force of a Super Middleweight in a real match was 866.6 N. A different study found that a punch with a force of 4,096 N would accelerate a target's head at 53 g (53 times the force of gravity). The Straight Dope highlights some of the ways that getting punched is bad for you:

[B]oxing is a punishing sport, especially where the head is involved. Damage comes from three things: (1) the impact itself, which may be manifested in, say, a broken jaw; (2) acceleration to the brain leading to abrupt contact with the skull, possibly resulting in concussion; and (3) the rotational force that twists the brain within the skull, increasing the severity of injury and the likelihood of a knockout.

Citing the Wayne State Tolerance Curve (below), the same article says that any impact greater than 50g has the potential for serious brain injury. And you're talking about impact forces that could greatly exceed that. So to answer your question, an unarmored human getting hit that hard would be in for a bad time.

What is gonna happen with Hero if he hits solid wall from stone?

What would happen if a normal human punched a stone wall? You might get a boxer's fracture (see below x-ray). In other words, you break your hand. So what happens if someone punches a wall really hard? You'd really break your hand.

5000J will lift 100kg at a height a wee bit over 5m. You can do it slow, like a weight lift or you can do it with a sudden intense acceleration followed, hopefully, by a free-flight of that body to that 5m height - if and only if both the hand and the body are tough enough to withstand the impact.

So, what it would be to have a punch that connects with the $$m = 100kg$$ body over a distance of $$h = 0.1m$$, with a total energy cost of $$E = 5000J$$? What force would it be required?

At the end of acceleration phase, the energy of the body will be: $$E = E_p + E_k = m h g + m v^2/2$$ and thus the speed will be $$v = \sqrt{\frac{E - m h g}m} = \sqrt{(5000 - 100 \cdot 0.1 \cdot 9.8)/100} \frac ms = 7 \frac ms$$

That speed is reached over a time of $$t_{acc} = \frac {2h}v$$ (about 29ms) , which leads to an acceleration of $$a_k = \frac v{t_{acc}} = \frac {v^2}{2h} = \frac {E-m h g}{2 m h} = \frac E{2 h g} - \frac g2$$

Now, the total force to create $$a_k$$ acceleration against gravity will be $$F_t = m\cdot (a_k + g) = m\frac E{2 m h} +m\frac g2 = \frac E{2h} + m\frac g2$$

Simple. So, a punch that connects with the 100kg body and imparts 5000J over a distance of 0.1m against gravity will require a force of $$5000/(2\cdot 0.1) + (100 \cdot 9.8)/2 = 25490 N (= 2601 kgf)$$ (the weight of 2.6 metric tons)

At this kind of force applied in an uppercut against the opponent's jaw, the results will likely be:

1. the jaw is driven into the skull and the so mutilated head of the opponent will dangle on top of a shattered neck
2. the bones of the hitting hand will present themselves to the avid viewer under the form of shards sticking through a perforated skin