# What would be the physical effects of a fistpunch with greatly magnified strength? [duplicate]

Assume a humanoid with greatly increased strength. He (or she) throws a massive direct punch at the middle of the breast of a human, who is standing in range.

Assume a punching force of about 1000 KN.

Assume that the fist (and body) of the attacker are durable enough to make this work.

What is the effect on the body of the victim? Will the punch go directly through the body?

If you want to elaborate, these points are of great interest to me as well:

• Are there any interesting side effects?
• How would body armour (with plates) affect the process, if at all
• Would this ability be useful in ranged and melee combat? In modern combined arms battles or special forces scenarios.
• NEW: What role does the weight of the fist play?
• NEW: What does happen, if the punch lands on a tank for example? You may crank the force up for this. If the fist is hard enough, can it punch a hole in the frontal armour of a tank?

Trivia: I watched a lot of superhero flicks, and superhuman strength always sends the opponent flying. Now that I am about to include such an ability into a worldbuilding project, I am interested in what really would happen. Thanks!

EDIT: Thanks to Cort a clarification: The speed of the fist is at least an order of magnitude higher than it would need to be to avoid the victim's body to be able to "escape" the punch.

I was requested to "defend" this question. The Anathema already did a good job on that one. Thanks.

• I would have expected the momentum would be more relevant to answering the question than the force (since force varies with time during the contact period), but this article on what sorts of blows will break bones does state limits in terms of forces rather than momentum. Mar 30, 2016 at 20:41
• You may enjoy this related video by Vsauce: What if Superman Punched You? Mar 30, 2016 at 20:53
• Another related video by Vsauce: What Would Happen If You Were Dragon Punched? Mar 30, 2016 at 21:37
• @MichaelKjörling + close voters - the utility of that super strength punching and the effects of that strength are two separate ideas. I don't believe that's a duplicate. That the OP in that linked question wrote a bonus of "how hard" (which is the only thing that comes close to being related to this) is something I'm not really enjoying. I don't believe we should write a bunch of "bonus questions" which might (for good or nebulous reasons) invalidate future questions of fun and valuable content, either, but that's a separate issue. Anyway, my point is that I disagree. Utility != effects. Mar 31, 2016 at 17:05
• @TheAnathema While the question linked as duplicate may not actually be a duplicate question, the top answer of the linked "duplicate" essentially answers the questions in this question.
– Aify
Apr 1, 2016 at 5:42

"It depends" Surprisingly it depends more on the opponent than the one throwing the punch.

Depending on circumstances, it could tear straight through (that is 100 tons of force!), or it might just push the opponent back. Certainly the opponent won't get the opportunity to say no.

By Newton's third law, if your hero can punch their opponent with 100kN of force, their opponent must be able to exert 100kN of force in the opposite direction. How they do that depends on their body. Take an example where they are up against a wall when this happens. They'll exert their 100kN of force by exerting 1000kN of force against the wall, holding them in place. In this case, the punch will have an effect worthy of any B-rate horror flick, because the only thing left to give is their body. Armor wont have any effect at all unless it is rated to withstand the combined weight of 2 M-1 Abrams tanks resting on it.

However, in the case where they can move, the story is a bit different. You can only exert 100kN of force if they can exert a corresponding amount of force back. If the punch is slow enough, you can punch with "up to" 1000kN of force, but you find yourself limited by the opponent moving backwards in response. Intuitively, if you were up against a hydraulic ram which was used to slowly bend steel tank armor, it would move slow enough that you'd get out of the way. The ram would never reach maximum force. To reach maximum force, you have to strike fast. That's where it starts getting interesting.

I say it gets interesting because the more agile your opponent is, the faster you're going to have to strike to achieve 1000kN. Striking a mosquito with 1000kN may require punch speeds far in excess of mach 1, because the mosquito has to be accelerated remarkably fast before F=ma can reach 1000kN. Fast accelerations are caused by high speeds with respect to the target's ability to respond.

If your punch ever exceeds the speed of sound in the opponent's fleshy chest, things start to get strange. You start to see shockwaves because the information about your punch cannot reach the opponent's extremities fast enough. This permits all sorts of strange sheering effects. I've heard NASA has some interesting videos of what hypersonic collisions look like.

If you're limiting yourself to human speeds for the punch, you wont be able to reach 1000kN without something like a brick wall behind your opponent. As a result, they will be exactly as unhappy as they set themselves up to be. A highly skilled martial artist may be able to react in a way to convert most of the energy into backwards motion for his entire body. A less skilled fighter may not, letting a massive amount of energy strike the front of his chest against the further back parts of his chest. His heart will not be happy.

Edit: given the clarifications we can explore more. If we assume the punch is fast enough that the recipient cannot get out of the way, the next layer of the question is pressure. How much pressure can you exert with your 1000kN of force, vs how much pressure can the object endure? The key for this is a concept known as "yield strength" this is a knee in the "stress-strain" curve. Below the yield strength, something will typically rebound back into its previous shape. Above that yield strength, it will permanently deform plastically.

You can do a lot of damage here with these forces. Take 4" rolled steel tank armor, used during WWII. It's yield strength is 688.5 MPa. Any pressure above that will permanently deform the steel in some way. If you have 1000kN at your disposal, you can deform the steel as long as you concentrate that force over 12 square centimeters (1000 kN / 950 MPa = 10.52 cm^2). The front surface of my fist is about 30 cm^2, so I couldn't quite damage the steel with the whole surface, but if I focused on my knuckles I could easily put a dent in 4" rolled steel. If I had sightly more force at my disposal, like 3000kN, I could actually put fist shaped indents in steel. If I could somehow sustain that 3000kN for the length of the entire punch, I could either severely dent that armor, or rip straight through, depending on the physics. The only real limit is the point where I move the tank rather than punch through it, which you explicitly took care of in your edit.

Now you can imagine the chunky salsa that will occur if we repeat that experiment with a human that doesn't get out of the way of this blow in time.

• Nice. The other issue (too lazy to write an answer) is that if you hit with your fist someone in the face with 1000KN of force, then that someone is hitting you with his face in your fist with 1000KN. So the man launching the punch needs to be bolted to the ground, too. Mar 30, 2016 at 22:22
• Thanks to this comment I've found that my prior worldbuilding already provides a solution for the reaction problem :) Now everything shifts in place.
– user6415
Mar 31, 2016 at 0:08
• @openend Updated to include the tank numbers Mar 31, 2016 at 1:27
• @MichaelKjörling there is a difference between "durable" and "secured to the ground". Mar 31, 2016 at 7:20
• @SeanR That would depend more on whether the punch has to break the speed of sound in steel to achieve 1000kN, creating shockwaves. Really, there are enough phsyical limits being handwaved away to create this force that I'm wary to say anything about the second order effects like that. Mar 31, 2016 at 18:10

So the physics of superhero movies is shall we say...not accurate.

That much force applied to a solid object, say a block of wood or metal would likely send it flying as bodies tend to in a movie.

If on the other hand you are punching something squishier or even things more brittle it simply wouldn't work that way.

If you punch a person that hard at the very least it would completely cave in the chest cavity if not outright penetrate the body. That would absorb a lot of the force and while the body (in the case of chest cavity crushing) would still fly backwards it wouldn't be nearly as far or dramatic. If the force was strong and fast enough to puncture the torso the body may barely move backward at all.

Getting away from bodies things like concrete or even stone would be likely to fly a little but in much smaller pieces, the stone wouldn't fly as a whole but rather as a bunch of sharp quick moving projectiles and they would fly in various directions as the force would enter the stone and go both forward and sideways.

The short version is what you punch will determine what happens.

Moving on to your more specific questions.

Are there any interesting side effects?

Not particularly no. The biology would have to be radically different for this humanoid to exist which can have whatever side effects you want really. The only required side effect would be a necessary increase in body density. So they would be significantly heavier than a normal person, otherwise punching something that hard would send them flying backwards.

How would body armour (with plates) affect the process, if at all

This has been addressed in some other questions namely this one. At a certain point armor ceases to be effective as the force will kill the person in the armor no matter how strong it is. Humans can only take so much force before they squish...hence Iron Man...while awesome is completely impractical.

Would this ability actually be useful in ranged and melee combat? In modern combined arms battles or special forces scenarios.

In antiquity it would have been very obviously beneficial, swinging a giant sword, punching a cavalry charge in the face, using a ballista as a longbow...you get the idea. In modern combat the biggest benefit would be their nearly invulnerable frame and skin...if weapons can't penetrate them well then you are going to have a hard time, but skills like this would be wasted on a standard grunt.

On the other hand these individuals would make amazing special operations forces. Helo airlift may prove a challenge with their added weight but other than that these guys could do serious damage on the covert side of things.

As a side note if they were air dropped in the parachute would have to be massive...I suggest night ops lol.

Striking that hard and fast would have the same effect as shooting a cannon ball through them. You'd be standing there with your arm up past the elbow stuck through their chest.

Any form of impact works by accelerating the tissue impacted. If the acceleration is slow enough that the tissue can absorb and disperse it then there is little motion of the target although it might do enough internal damage to kill.

If the acceleration is slow enough that the tissue can absorb it, but the impactor has large momentum, then you have shove, which accelerates the entire body along the spatial vector of the impactor.

If the acceleration produced by the impactor is so fast that the surrounding tissue cannot stretch or flex to absorb it, then the tissue tears. If the impactor has enough momentum the tearing continues all the way through the body. That how a bullet does damage.

The rule is that the smaller the impact surface relative to the momentum of the impactor, the less energy gets transmitted to the target. Two objects with the same velocity but with different areas of impacts will have different effects. Getting hit by a 50 gram ball of aluminum foil 20cm wide going at 200kph will sting a bit. Getting hit by a 50gram needle of aluminum with an impact area measured in micrometers will punch a hole through you so fast and clean you won't know you've been shot.

No bullet or shot of any size will knock a person backwards. All the energy in firearm projectiles are so concentrated they destroy only the tissue along their flight path ripping it away from surrounding tissue without accelerating it. People who get shot just drop.

I shot a lot of animals in my childhood on the farm from squirrel size to deer and they all drop. Made a long range shot with a deer rifle at a squirrel once just so see if I could hit it. I did and the bullet punched out a big hole and the rest of the squirrel just dropped out of the tree in a blizzard fluff, much to the confusion of my dog.

So, if you start hitting people with the momentum per impact area of a firearm projectile, the effects will be the same.

1000 kN of force, applied fast enough that the target isn't just "moved back" by it. Let us assume that this means that the punch force extends over about a chest-thickness -- 20 cm -- to get an idea of what happens.

This is 200 kJ.

If the energy was turned perfectly into kinetic energy over an entire 100 kg target, we get 63 m/s, or 227 km/h.

f = ma; 1000 kN / 100 kg is 10 km/s^2, or ~1000 gravitates of acceleration.

63 m/s / 10 km/s^2 is 0.0063 seconds. Which means the fist is moving at an average of about 32 m/s or 114 km/h -- in practice, the fist will have to change speed to provide a uniform 1000 kN force. (a fist that moves at a fixed speed, without any give, regardless of what is in its way, will inflict unbounded force)

So if the target was wearing perfect body armor that distributed the impact over the entire body, and used fluid to keep pressure up -- the target would probably still die. The highest g-force survived by a human is 214.

Without the super-armor, you can approximate this by driving at high way velocities and throwing a lead fist-sized ball at someone. That won't work perfectly, because it will be slowed down by the impact. But it is an experiment Mythbusters can do.

Alternatively we can do math: Bone has a shear strength of ~50 MPa -- if the fist is 30 cm^2, 1000 kN is ~1E11 Pa, or 100 MPa. Flesh has less shear strength than Bone, so the fist won't pull the rest of the target along -- it will penetrate.

We could presume that about half of the force will spread as it shears through the body, and the rest will "pop" through. So you'll end up with your fist sticking through a body that is flying away at about 44 m/s or 160 km/hour.

Ick.

The G-forces suffered by the rest of the target in this situation are about 600 Gs; so even if the fist-sized hole didn't kill you, you'd be dead.

On a tank, 1000 kN of force on 54431.1 kg generates 2 Gs of acceleration. Over 1 meter (the length of an arm), a rigid tank is accelerated to 6.1 m/s, or 21 km/h. This will look more like a hard push than a punch; tanks are HEAVY.

Modern tank armor can take the pressure you are putting without massively deforming. The mounting system may be stressed, as tanks are not meant to be picked up and pushed around by their armor plates.