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In a story I’m writing, there’s a superhero who uses a magic spell to increase the strength of her body. This means that her body becomes more durable as well. As she increases her capacity to output magic, her strength increases as well. Over the course of her crime fighting career, she will have to contend with bullets. But as she gets stronger, they will have less and less of an effect on her. I have three specific scenes in my head where she shows her resistance to bullets:

  1. She is shot at with a standard assault rifle, but due to the durability of her body, the bullets are unable to reach her vitals, only burying themselves about half an inch deep into her flesh.
  2. She is, again, shot at with an assault rifle, but this time the bullets bounce right off, having about as much effect on her as nerf darts.
  3. She is shot in the face with a high-caliber sniper rifle round, but she catches the bullet between her eyelashes.

My question is, if every part of her body is enhanced proportionally by her spell, and she can lift around 280 pounds when not powered up, how much would she be able to lift at most in each of these instances?

Edit: to clarify, this spell proportionally increases the strength of every part and aspect of her body, and that includes the toughness and tensile strength of her skin and flesh. I’m asking that you multiply the strength of normal human flesh to the point where bullets would have the effect I’ve described, and then take that same multiplier and apply it to her physical strength.

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    $\begingroup$ Not sure how one can translate durability into strength. Homer Simpson for example can take a punch like few can but he is not very strong at all. $\endgroup$
    – Willk
    Nov 9, 2021 at 22:32
  • $\begingroup$ As I understand it, it's not raw-strength that stops people being stronger than they are, but that pain limits the effort. As Willk sais, what's the toughness/strength relationship, how does that work? $\endgroup$ Nov 10, 2021 at 0:04
  • $\begingroup$ We don't know how an increase in being bulletproof translates to an increase in physical strength; that's something that you can make up as you please. $\endgroup$
    – KEY_ABRADE
    Nov 10, 2021 at 2:01
  • $\begingroup$ Recommended research on rifle bullet penetration $\endgroup$ Nov 10, 2021 at 18:15

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If we assume your character is an average 140lb female athlete, then a normal strength would be something like.

  • Bench-press: 40kg
  • Squat: 60kg
  • Deadlift: 72.5kg

These values are well above general population female averages, but since she cares enough to be a crime fighter, I will assume she is not on the couch potato side of things.

Scenario #1:

A standard, non-armor penetrating anti-personnel round is typically rated for about 12-18" of pentation against ballistic gel. Depending on gun and ammo type you could see a LOT more pentation than this, but I will use 18" as a basic starting point since assault riffles are generally designed around higher penetrations. So, lets call this 32x strength. This would result in:

  • Bench-press: 1280kg
  • Squat: 1920kg
  • Deadlift: 2330kg

This is just strong enough to lift most cars.

Scenario #2:

The average assault riffle hits with about 1000 foot-pounds of force. An average nerf dart hits with 0.16 foot-pounds of force. This means we can assume you are at about 6250x strength.

  • Bench-press: 250,000kg
  • Squat: 375,000kg
  • Deadlift: 453,125kg

Scenario #3:

We can pretty much stop measuring strength here for most practical purposes. By the time you get anywhere near this strong, adding more strength has absolutely no additional affect in most situations. Her feet will always sink into whatever ground she is standing on long before she can lift anything near this heavy, and the weight of her own body and lack of surface area means she will never achieve enough friction or counterweight to make any meaningful use of her full strength. She may in theory be strong enough to punch through that steel vault door, but all it will achieve is throwing herself backwards

... at least this was my original hypothesis, so I decided to try to calculate out the maximum size, maximum toughness obstacle your hero may ever need to overcome.

The hero will be best be able to exert her strength when trying to pull something apart or crush it between her hands, because this gets around her limited inertia issue. So, let's say a bad guy considers this, and decides to attack her with a killer robot armored with Boron Composite Fiber. BCF is not necessarily the the best material for stopping a bullet, but when it comes to tensile and compressive forces, it is some amazing stuff. It has a tensile strength of about 4GPa, and a Compression Strength topping out at somewhere around 6GPa, this stuff is REALLY hard to ripe or crush.

Our normal female athlete can butterfly curl about 30kg which is probably about her maximum crushing power. If we assume she is using the full surface area of her palms to crush this thing, she needs to exert her force over about 128cm^2 (54 per hand). Since GPa is measures by the M^2 and lift weights are measured against gravity, this means we can estimate she can crush pretty much any man made object with about 260,000x human strength (aka:~41 times as strong as scenario #2)... so turns out there is a use for greater than Scenario #2 strength after all, even though it is rather niche.

So, can catching a bullet with eyelashes girl do it?

unfortunately, this is a really hard question to answer since I can't find how much force it takes to bend an eyelashes, but... it may not matter. We do not know how much your hero catches the bullet by when she blinks it out of the air; so, you can easily say at this point she is at least 41x as strong as needed to nerf gun bullets off her skin, and that no material on Earth can actually restrain her.

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  • $\begingroup$ I would argue that instantaneous applications of strength would still yield effects. punching the vault door at a significant speed would cause both the floor and steel not enough time to move for use as leverage (or if fast enough annihilated directly into plasma) $\endgroup$
    – IT Alex
    Nov 10, 2021 at 21:17
  • $\begingroup$ @ITAlex "if fast enough" is the key point here. The OP made no stipulations about super human speed. $\endgroup$
    – Nosajimiki
    Nov 10, 2021 at 21:33
  • $\begingroup$ Vault doors can be used for leverage against themselves. If both hands can get a purchase and pull away from each other, she should be able to open it like a bag of Doritos. $\endgroup$
    – John O
    Nov 11, 2021 at 17:18
  • $\begingroup$ @John, depending on the design of the door, this may or may not be true. I was picturing a scenario where the frame is wider than she can reach, and there is no significant gap she can fit her fingertips into. A 140lb person can not just press their fingers in to make a gap where it does not exist, this just pushes their own body backwards. $\endgroup$
    – Nosajimiki
    Nov 11, 2021 at 20:20
  • $\begingroup$ @Nosajimiki I'm assuming that there is a handle or something like it on the door, that it's not smooth and featureless. I did qualify my statement with "if both hands can get a purchase". But honestly, I haven't carefully inspected many vault doors lately, so [shrug]. Agreed though, it's all about being able to pry outward, and she does need a gap or concavity of some type (and maybe some chalk). $\endgroup$
    – John O
    Nov 11, 2021 at 20:39

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