10
$\begingroup$

I have a person with a superpower to interact with the world as though they were extremely heavy. The power is smart and selective, which allows him to walk normally without crushing the ground, or other undesirable effects.

I want him to be able to casually (at a normal walking speed, let's say 5km/h, without being significantly slowed) walk through a brick wall (or a similar wall that would be used as an external wall of a large residential building), but I'm not sure how much weight would be required to do so, and what the effects would be for his other interactions (eg. when punching stuff).

I can calculate his momentum/force, but I have no idea how much force would be required to break through a brick wall, or where to find that information.

I have found questions about punching through a wall, but they focus on superstrong (or more precisely superfast) punches by someone with normal weight.

Improve this question
$\endgroup$
13
  • 5
    $\begingroup$ Speed doesn't matter because, at 5 km/h, the character isn't relying on momentum to generate the force to break through the wall. Mass/weight doesn't matter because the force of gravity is straight downward and therefore doesn't affect the wall; to direct that force against the wall, they'd have to lean against it or something. So it's a little unclear what the question is asking? $\endgroup$
    – GrumpyYoungMan
    Nov 19, 2021 at 3:47
  • 11
    $\begingroup$ @GrumpyYoungMan well, if the man has the weight of a freight train, the momentum would matter a lot even at 5 km/h. $\endgroup$
    – Alexander
    Nov 19, 2021 at 3:58
  • 3
    $\begingroup$ Find something you know can break through a brick wall. Then go $mv = $mv where the LHS is the thing you find and the RHS is a moving at 5 km/h. $\endgroup$
    – DKNguyen
    Nov 19, 2021 at 4:08
  • 6
    $\begingroup$ The issue with this kind of science-based questions: a calculation is required, which depends on the wall and the quality/strength of the wall. You may find calculations on line for a specific brick wall, not any brick wall. Without an accurate description of the wall involved, you can't say anything science-based. Is this an antique wall ? A new wall ? How thick is this wall... what cements are used.. $\endgroup$
    – Goodies
    Nov 19, 2021 at 9:36
  • 2
    $\begingroup$ Our heavy person might be able to walk through a brick wall, but they'd be flayed in the process. $\endgroup$
    – Tony Ennis
    Nov 19, 2021 at 18:14

3 Answers 3

Reset to default
17
$\begingroup$

To do a casual back-of-the-envelope estimate of going through a wall based on momentum at 5 kph:

  • Table 6 of https://www.sciencedirect.com/science/article/pii/S1018363921000155 estimates the horizontal shear strength of a cinder block wall at 0.43 megapascals (approximately 4.4 kg per square centimeter).
  • A table found on a body surface area estimator page (by Jove, the Internet really does have everything, doesn't it?) at https://www.calculator.net/body-surface-area-calculator.html?csex=m&bodyweight=155&bodyweightunit=pound&bodyheightfeet=5&bodyheightinch=9&bodyheight=&x=63&y=12 suggests that the surface area of an average adult male is 1.9 m^2. A coarse guesstimate of the frontal contact area is about 40% of the total so that yields 0.76 m^2
  • Total force required is the product of the required pressure and the contact area, giving us 326,800 newtons of force.
  • Force is mass times acceleration, only in this case, the person is decelerating as they contact the wall. We choose a (rather arbitrary) 0.1 seconds to decelerate when they contact the wall at the stated 5 kph velocity, justified only by the assumption that the human body is a bit squishy, giving us a ~13.9 m/s^2 deceleration. Plugging that into the force formula gives us an estimated minimum of slightly over 235 metric tons of mass required.

I'd probably multiply that by 2 or more, both to paper over any inaccuracies in the estimate and to make the action seem effortless, as the question asks.

Improve this answer
$\endgroup$
13
  • 2
    $\begingroup$ Now do it considering the brick is set together with mortar and the shear strength of the mortar may be the "weakest link" in the structural integrity of the wall. A review in the sciFA of shear strength of mortars at researchgate.net/publication/… $\endgroup$
    – Adrian Colomitchi
    Nov 19, 2021 at 6:32
  • 1
    $\begingroup$ @AdrianColomitchi I did look at that but it's difficult to determine which values from it to use; the conclusion itself is that the formula they were evaluating doesn't match empirical results and that more research is needed. If I instead look at Table III of brick.com/sites/default/files/pdf/tsd088.pdf on flexural bond strength (the shear strength in Table II doesn't seem appropriate) and do an eyeball avg. of type N and S masonry cement (which appear to be the appropriate types), I get about 0.27 MPa, or about 35% of the strength of the cinder blocks. $\endgroup$
    – GrumpyYoungMan
    Nov 19, 2021 at 7:12
  • 8
    $\begingroup$ This seems very high ... cars and vans can go through walls whilst parking. I think the shear force of the bricks is irrelevant, as you're not shearing the bricks, you're shattering the mortar. $\endgroup$
    – Dan W
    Nov 19, 2021 at 11:51
  • 2
    $\begingroup$ @GeorgeMenoutis yes, but a walking man is continually applying force to keep walking as they’re not rolling on wheels like cars. $\endgroup$
    – Dan W
    Nov 19, 2021 at 13:10
  • 2
    $\begingroup$ "326,8700 newtons of force" — what is comma meant to represent here? Is it decimal comma or digit grouping comma? In the former case it's inconsistent with other numbers in this post which use a decimal point, and in the latter it's strange to see grouping by four digits instead of the usual three... $\endgroup$
    – Ruslan
    Nov 19, 2021 at 21:37
7
$\begingroup$

I don't know how much extra weight is the minimum that your character's superpower will have to simulate to enable them to break through a brick wall at a normal walking pace.

But I can suggest that a simulated weight in the weight range of elephants should be sufficient to break through a quite strong wall, even if not necessarily to walk through the wall.

I once found a century or so old article reprinted on the internet where a circus man wrote about elephants. He mentioned a fight between two bull elephants in the elephant barn of the circus's winter quarters. They fought until one elephant's tusk broke off and the other one pushed him through the brick wall, 14 inches thick, of the elephant barn. Despite the vast amounts of blood they shed, both elephants had only minor injuries except for the broken tusk.

And in another article I read about a contemporary villager in India who was injured by a flying brick when a hungry elephant broke a hole in the wall of his house and reached in to grab a bag of rice.

And in another century old article I read about a circus parade in an American town where the elephants were stampeded by a barking dog and ran through the front wall of a wooden house, through the house, and out through the back wall.

So I looked up more such stories just now.

Here is a link to a video of elephants passing through a gap in a concrete wall.

https://www.youtube.com/watch?v=yUf2KltOc7s

Here is a link to a video of elephants destroying a wall:

https://www.dailymail.co.uk/news/article-4628602/Panicked-elephants-break-boundary-wall.html

https://www.theguardian.com/world/2021/jun/21/elephant-in-the-room-visitor-crashes-through-kitchen-wall-in-thailand

https://www.naturalhistorymag.com/picks-from-the-past/081596/the-elephant-in-captivity?page=3

p. 73 here:

https://books.google.com/books?id=Yk09AwAAQBAJ&pg=PA73&lpg=PA73&dq=elephant+pushes+elephant+through+brick+wall&source=bl&ots=ssIPiyqSjQ&sig=ACfU3U3DpRyj12BusHP5lYyMtNk6ERFxmA&hl=en&sa=X&ved=2ahUKEwj5vb-3wKP0AhXcSTABHQXlB6kQ6AF6BAgbEAM#v=onepage&q=elephant%20pushes%20elephant%20through%20brick%20wall&f=false

https://books.google.com/books?id=f4PzAAAAMAAJ&pg=PA412&lpg=PA412&dq=elephant+pushes+elephant+through+brick+wall&source=bl&ots=LPDDgAYGK8&sig=ACfU3U0hx6gt1_YAeR4SQ67XCRheehhN8Q&hl=en&sa=X&ved=2ahUKEwjf3OqexqP0AhUgSTABHT9-CGkQ6AF6BAgbEAM#v=onepage&q=elephant%20pushes%20elephant%20through%20brick%20wall&f=false

https://www.asesg.org/PDFfiles/2021/53-47-Sahu.pdf

https://news.mongabay.com/2021/07/sri-lanka-seeks-peace-with-pachyderms-as-human-elephant-conflicts-escalate/

And if you don't think that mere elephants are heavy enough to simply walk through strong walls at a normal pace, just give your character simulated weight that is twice a much as an elephant, or 5 times as much, or 10 times as much, whatever seems to be sufficient.

Improve this answer
$\endgroup$
1
  • $\begingroup$ 14 inches thick is probably three wythes. If it was only two, an elephant would probably notice some deflection if they bumped into it. As soon as there's a hole for their head, the rest below it just falls over with minimal effort. When you demo a brick wall the only hard part is the first brick. $\endgroup$
    – Mazura
    Nov 20, 2021 at 1:52
2
$\begingroup$

Unless your character is supernaturally durable there is no weight that will allow them to walk through a brick wall and survive. Brick walls are very sturdy. If you don't believe me find a brick and try giving it a solid thwack. Notice how that hurts. Notice how the brick doesn't seem to care. A well built brick wall will require many burly construction workers swinging sledgehammers with all their might to bring it down over the course of an afternoon. A human hit square in the chest with a sledgehammer will need to go to to the hospital for broken ribs or worse.

To look at it another way even when protected by a modern car, with seatbelts, airbags and engineered crumple zones if you crash into a wall you will be having a very bad day. Now imagine crashing into the same wall without all that added protection.

Improve this answer
$\endgroup$
2
  • 2
    $\begingroup$ I've seen a pair of (or three?) (des?)construction workers bringing down a brick wall in minutes, with sledgehammers. Maybe half an hour. $\endgroup$
    – Pablo H
    Nov 19, 2021 at 15:10
  • 3
    $\begingroup$ @PabloH I guess it really depends on the size of the wall, and whether it's a façade, or free standing. The point is that a brick wall can withstand significantly more sledgehammer blows than a human can. $\endgroup$
    – sphennings
    Nov 19, 2021 at 15:26

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .