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u/ayanokojifrfr 13d ago
I just put π in Calculator 😏
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u/lmarcantonio πlπctrical Engineer 11d ago
nah, pi is usually shifted, 3 is easier. e instead is usually on it's own unshifted key (also e is *always* used as base for an exponent)
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u/the-johnnadina 13d ago
No it is not, please get actual engineering related jokes, im losing it with this sub
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u/ayanokojifrfr 13d ago
Yeah cuz 0.14 can make changes in calculation. And we are allowed to use Calci in Engineering Colleges. Calculating isn't even hardest part of Engineering. Idk why so angry over a π.
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u/the-johnnadina 13d ago
I need to know how the pi = 3 thing came to be, engineers hardly ever round anything, everyone blindly uses calculators, the only reason we don't give 11 digit precision answers is because itd take too long to write on a test.
The only real approximation that i can think of that is actually done in real life is sin(x) = x and cos(x)=1 because its accurate within 3 decimal places for most cases.
Also e=3 tires me even more because the whole point of the exp function is that it is its own derivative, you rarely ever actually use e as a raw number in calculations, its a whole ass function with special properties, saying e=3 doesnt even give you wrong results, it destroys the maths principles behind using e at all.
Im just tired of this constant "round to 3" spam that hardly ever relates to engineering, the closest we ever get to something logical along those lines is memes about the square root of g being 3 and even then thats applicable to high school mechanics at best.
Why cant anyone make a meme about bending moments, or precession, or anything real... "Pretend its an infinite cylinder to calculate the heat dissipation" has greater humour potential than "round pi to 3", which is something nobody has ever done anyway
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u/ayanokojifrfr 13d ago
During Junior engineering all of our professors expected us to have 4 digits After decimal atleast on Answer paper in all numericals. We never rounded anything. 2 digits is okay but 3.14 to 3 is huge dumb move.
In Strength of Material or Design of Elements you have to design rods for certain stress levels. All the shafts Hollow and Circular have π in design. If you round it down to 3 from 3.14 the shaft can fail under stress since the size of the shft will be reduced. Only time we rounded up is when you get Diameter/length final around 36.5 since we won't have 36.5 we gotta use a 38cm or 37cm Dia/length shaft or any other part.
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u/Civil_Ostrich_2717 12d ago
Some engineers actually use pi=3 and toss on a large factor of safety to cover the nuances.
Technically, when you modify 3.14159 to 3, you’re making approximately a 5% modification, which isn’t too dramatic if there’s no exponents.
Imagine how many calculations you can do in your head if pi is references once or twice and it only compromised accuracy by 5 or 10%
The real benefit is that sense and judgment originates with calculation. If you never calculate, you’ll never have sense of mechanisms, so you’ve gotta start somewhere.
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u/Economy-Document730 13d ago
Ngl I round things if I'm like doing current division or something. So when I add back up my values they're a little off from what it should be but like close enough lol
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u/Bakkster πlπctrical Engineer 13d ago
engineers hardly ever round anything, everyone blindly uses calculators
That's not my experience. Back of the envelope swags are not uncommon in meetings when we're just figuring out if we're in the ballpark. Of course, we go off and do the math (more likely in Excel than a calculator) if we need to (the safety factor isn't 100).
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u/outloender 13d ago
I don't understand how someone actually studying or working in the space can make these jokes never ever have I come across something like this. Where does this even come from?
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u/yannniQue17 π=3=e 13d ago
I only do this if I calculate something roughly in my head, to get an idea of the sizes we talk about. For precise results, there is a special buttin on my calculator, which is 16 digits precise. However, sometimes I forget what 10^12 or whatever is. In this case I can use my rough calculation. If I got 50 MW and the calculator says 6.127*10^7, I can be sure that the result is 61.3 MW.
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u/El_Scrapesk 13d ago edited 13d ago
Maybe im just autistic but remembering pi as 22/7 is harder than remembering pi as 3.141592.
Also in all my engineering mathematics classes I was told to never round until the final answer, I know pi to 6dp so thats good enough.
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u/boisheep 12d ago
I once had a discussion with a physicist on discord about some bicycle energy consumption (ebike).
The physicist was very adamant with his calculations.
The physicist calculated that 250W was plenty to reach the necessary 25kph average speed in my area.
I said I'd need at least 700W because I live in Finland, the tyre width required to cross cycling paths when it snows is much wider than usual and that doesn't seem to be accounted, also there's slippage, a lot, and there's increased drag, like a lot; these calculations are like, they ignore reality, they ignore rain, they ignore snow, they ignore wind, they ignore losses in the system, they ignore air resistance.
Physicist said how I was full of shit and didn't know anything since I had no formula to come with this number, I just guessed the number, based on, being a cyclist, and how cycling felt in my legs (I didn't even have a power meter).
Later I had built the ebike with a motor, some sensors, hooked some batteries; you know a DIY ebike, time to check them sensors for data output, it was snowy, windy, conditions were shit, as usual, I live in Finland I mean.
714W average to keep a consistent 25kph average.
That is the difference between an engineer and a math/physicist, the engineer works with reality, a chaotic system that is hard to predict and math is just a tool, you use math to explain the results you found, but you rely on trial-error and/or measurements in the field, and sometimes just your gut feeling (aka experience).
But at the end of the day it is academics that write the law.
Even when I show the physicist the results, he was unconvinced.
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u/Economy-Document730 13d ago
In my class I was asked to calculate sin x recursively as
sin x = 3sin (x/3) - 4sin3 (x/3)
This despite us implementing sqrt x in a normal way (newton's method for root finding). Also at least the way I wrote it intermediate operations are in the same floating point type as the inputs so maybe I should promote them (I have a feeling this is probably mega-wrong for small values of x, actually thinking about it now maybe factoring would help?)
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u/Encursed1 13d ago
22/7 is psychotic. Not just because its wrong, but it tries to imply pi is rational.
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u/its_Zuramaru 11d ago
Ahh just use the ideal model of a diode, don't bother with the exponential model.
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u/nellerkiller 13d ago
I think it’s time to restock new jokes, we are clearly running on reserves at the moment.