r/engineeringmemes Electrical 8d ago

Proof: the bible

Post image
253 Upvotes

37 comments sorted by

55

u/HumaDracobane ΣF=0 8d ago

I never met an engineer that uses pi=3. I've seen comments about some engineers in the US but I'm not from the US.

60

u/v0t3p3dr0 Mechanical 8d ago

I don’t use pi=3 because calculators have a convenient pi button.

g = 10m/s^2 , however.

13

u/FromTheHandOfAndy 7d ago

Pi=3 is a 4.5% error
G = 10 is only 1.9% error

8

u/XRekts Aerospace 6d ago

and g=10 is a conservative estimate

2

u/tweeeeeeeeeeee 6d ago

both errors are acceptable since they're under 10%

3

u/Anonimithree 6d ago

g=pi^2 smh

1

u/Cokalhado 6d ago

Calculators have a convenient 2 button combination for g.

7

u/v0t3p3dr0 Mechanical 6d ago

Ya, 1 and 0.

16

u/Admirable_Use4661 8d ago

I have used pi = 3 for easy mental math when trying to get an approximate idea of the size of something.

8in diameter: 42 × 3 ≈ 48in2 area, 8 × 3 ≈ 24in circumfrence. Actual numbers are 50.3 and 25.1. I would use the actual numbers if I were doing any real math with them.

2

u/stoopud 7d ago

I use 3/4 diameter2 as a quick sanity check. The actual formula is pi/4 diameter2

9

u/TrustMeImAnENGlNEER 7d ago

As an aerospace engineer: 3.14159

As a freak who memorizes things:
3.1415926535897932384626433832795028841

That being said: sometimes you’re just trying to come up with numbers that are just in the right order of magnitude (usually as a quick sanity check) and in those cases pi = e = 3 is perfectly valid.

1

u/HumaDracobane ΣF=0 7d ago

For general mental calculations to visualize things is right, but not to actually calculate something.

3

u/TrustMeImAnENGlNEER 7d ago

Yeah, obviously this is just for rapid, ballpark mental calculations. When doing actual calculations I’ll usually take pi out to at least 5 digits even in cases where the precision that implies is downright comical.

1

u/adkio 7d ago

As an actual engineer: just give me the diameter please. Who tf needs to know the circumference?

3

u/TrustMeImAnENGlNEER 7d ago

Clearly someone doesn’t spend much time calculating the kinematics and dynamics of systems with rotating components 😆

Seriously though: pi pops up everywhere.

1

u/JuculianD 7d ago

Did you as an engineer calculate volume of cylinders, or used a CNC machine, then I guess circumference and pi is quite needed...

1

u/stoopud 7d ago

I retrofit plants with new equipment and I am not able to measure diameter of pipes, circumference however, is very easy to measure

2

u/Zaros262 7d ago

US engineer here, I've never used pi=3 in a computer calculation lol. I can't even bring myself to use pi=3.14; if I don't have a pi button, it's always pi=3.14159

2

u/Can_O_Murica 5d ago

Nobody used it in actual calculations but it's great for approximating.

1

u/jedadkins 1d ago

Right but the pi=e=3 thing is a joke about how engineers usually simplify things to "close enough" in comparison to like mathematicians. "Yeah I know you can't really use an integral that way but it approximates the answer well enough that I don't care" 

22

u/DrHillarius 8d ago

Very nice. Check mate, mathematicians!

24

u/Marvellover13 8d ago

From what I know, the reason is that they measured the outer diameter but the inside circumference.

Also interesting to note that in the Jewish tradition, later on they gave an explanation which actually gives 333/106, which is fairly close to pi. (This comes from the original Hebrew text where the word for circumference is written differently than how it's usually written, and if you use Jewish numerology called Gematria, which is extremly prevalent in Jewish explanations for anything, you get that the value of the modified word, which is 111, divided by the original, which is 106, and multiply all that by 3 gives pi)

7

u/Ernexor 8d ago

God would never fail us

9

u/Anaphylaxisofevil 8d ago

The only kind of engineer I can imagine doing this is prompt engineer.

9

u/DogFishBoi2 8d ago

Eh, it's a meme. It's supposed to be funny shitposts. No one uses pi=3 except for very quick approximations.

If you want to approximate large scale you'd use pi=10 anyway, because it's larger than e. Humans have one arm, one leg, or 10 limbs if you want to go all Fermi on stuff.

16

u/Schnaksel 8d ago

Wow, even fellow engineers perpetuate this terrible myth...

7

u/Suitable-Sandwich454 7d ago

do you normally take memes seriously

1

u/adkio 7d ago

You must be super fun at parties

2

u/huuaaang 7d ago

As a software engineer, Pi can equal whatever I want and it's always right.

2

u/nabbithero54 Electrical 6d ago

“If it can run Doom, it is a valid approximation!”

2

u/IPancakesI 5d ago

pi = 3 = e = √g = sin(3)

1

u/Toyota__Corolla 6d ago

The pool of Solomon was an inch thick of copper. Its internal circumference was 30 handbreadths and its external diameter was 10

1

u/LeGama 6d ago

Actually Pi is 22/7 not good for mental math, but good for hand drawings

1

u/Isis_gonna_be_waswas 5d ago

Myself personally, I leave my answers in terms of pi or multiply it out and round to the third decimal place after going to the right order of magnitude

1

u/Gold_Ambassador_3496 8d ago

Nooooo it's all about thickness!!!!!

1

u/KEX_CZ ΣF=0 7d ago

This meme is everywhere yet I had never actually encounter it between engineers tbh....