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What would a force of 172,500 Newtons concentrated into the size of roughly double the surface area of a fist do to a average late medieval knight in full plate armor? What would it do if it was directed upward into the person?

Changed things for misunderstandings

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  • $\begingroup$ Applied uniformly over this surface? We can assume that the material will not deform? The knight is wearing armor? Steel? Iron? Plate or chainmail? Is he sitting on a horse? $\endgroup$ – bendl Feb 13 '18 at 21:41
  • $\begingroup$ When we talk about an object hitting another we more typically know the velocity of the objects and their masses. A force is would be the reaction to the impulse. As written you are describing a constant force applied indefinitely which is not how a hit from e.g. a weapon or projectile would be. $\endgroup$ – StephenG Feb 13 '18 at 22:04
  • $\begingroup$ Is this one on-topic to be migrated to physics.SE? $\endgroup$ – Jakob Lovern Feb 21 '18 at 20:26
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Smoosh him flat from toe to hat

Spoiler alert: he doesn't survive.

172,500 Newtons is a lot of force. On Earth, the average human exerts about 600N of force on the ground. To exert 172,500N, you've gotta weigh nearly 20 tons. (38,700lb, or 17,500kg) And you wanna cram that into... Two fists? A back of my hand estimate (yes, literally) says that I have a punch area of 2 inches by 3 inches. Twice that yields 12 $in^2$, which transates roughly to .3048 $m^2$. This yields a pressure of 565,000 $Pa$, which is three or four atmospheres of pressure.

Delivered horizontally to a 600$lb$ knight over a period of 1 second, it would accelerate them from rest to 634.2 $m/s$, roughly mach 2. An immediate sonic boom would result, and they would be flung out of continued melee reach.

Delivered upward? 64.4Gs of force. Wikipedia says that:

A typical person can handle about 5 $g_0$ (49 $m/s^2$) (meaning some people might pass out when riding a higher-g roller coaster, which in some cases exceeds this point) before losing consciousness, but through the combination of special g-suits and efforts to strain muscles—both of which act to force blood back into the brain—modern pilots can typically handle a sustained 9 $g_0$ (88 $m/s^2$)

Needless to say, a 'typical medieval knight' isn't going to have g-force training.

But wait! There's more!

I assume that your knight is being uppercut to the chin in typical anime fashion.

Were this to be the case, the whiplash from this event would be severe, likely causing severe organ failure or death.

If that weren't enough, a bit more math shows that, using the same punch time and knight mass, but orienting up would launch the knight 20 km up into the atmosphere. On Earth, this is well into the stratosphere, coming with its own host of issues, namely the insufficient atmospheric pressure and the extreme cold (circa -60 degrees C,) to say nothing of the landing.

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  • $\begingroup$ 12 in2 is actaully 0.007742 m2 $\endgroup$ – Alexander Feb 13 '18 at 23:36
  • $\begingroup$ Oh, crap. That makes the pressure even worse. Have we reached the punch power of Saitama, yet? $\endgroup$ – Jakob Lovern Feb 13 '18 at 23:39
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    $\begingroup$ @JakobLovern No, as Saitama has as much punch power as he needs. ;) $\endgroup$ – Draco18s Feb 14 '18 at 1:04
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    $\begingroup$ Is it enough to justify a picture of him uppercutting some monster into oblivion? Because that's really all I want. $\endgroup$ – Jakob Lovern Feb 14 '18 at 1:11
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    $\begingroup$ No one will be launched anywhere, forces this large don't do things that typically make sense to us. Collisions like this act a lot like throwing a rotten tomato at a birthday cake $\endgroup$ – bendl Feb 16 '18 at 18:10
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Rounding up, 175,000 newtons over double a fist area (approximately 80 square centimeters) is about 22,000,000 newtons per square meter, or 3,200 PSI.

This amount of pressure applied to human tissue will result in immediate traumatic injuries. Depending on the location it can result in immediate death and dismemberment.

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172.5 or 172,500?

Because one is a sneeze and the other is being hit by a pickup truck going aprox 30mph. If 172,500 it would simply rip his head off or cave his ribcage in and probably send him flying a good distance to boot.

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