Lemmy Shitpost @lemmy.world SnokenKeekaGuard @lemmy.dbzer0.com 3 mo. ago

Guess I'll km/s

52 comments

In a parallel universe, someone is memeing about how teachers waste our time on useless stuff and never taught us to convert between units.
This is actually pretty important to being able to solve engineering problems in the real world. Invariably, every little sub industry has its own cursed unit system. And dimensional analysis is great for solving real problems on its own.

And if you get to a high enough physics level, they start setting hbar = c = 1 or G = c = 1, and you never have to worry about it again.

I'm the mean time, it's worthwhile to learn the trick to do this stuff fast-ish.
- I would like to introduce everyone to this video about cursed unit (youtube link warning)
  
  kWh has an intuitive reason. Watts are so small that you'd always calculate consumption in MJ and whatnot, and seconds are so short that you'd always be expressing time in ks. Using kWh will reduce the numbers to useful ranges and makes cancelling M and k unnecessary.
- I dislike that my highschool never once gave me the concept that units can simply be treated like constants to be cancelled out.
  
  I used to do the conversions for each variable before putting them in the equation like a fool.
  
  Now I'm slapping all of the conversions alongside the original values/units in a single expression like god intended.
- My thought as well. It's just wasting the students' time if they don't pay attention about the units - which basically all high-school physics is about.
Just divide by 3.6

Example:

10 km /h * 1000 m / km = 10,000 m /h

10,000 m/h * 1h/3600s = 10,000/ 3,6000 m/s = 10/3.6 m/s
- Shit like this is why we need metric time.
  
  don't speak like the french
  
  Shit like this is why metric needs to be replaced with a base12 system. Base10 is for children who still count on their fingers.
- I used to do it this way in highschool, but could never remember if it was divide by or multiply by 3.6
  
  Instead I now do it as you have shown, except it all goes in the same expression.
  
  10 km/h * 1000 m/km * 1h/3600s = 2.778 m/s
  
  No need for the extra steps. Slap it all in the same expression and put it in the calculator (being careful to check that the units cancel as intended)
  
  M/s is faster (lower number) than km/h so... That should give you enough explanation to understand whether you need to divide or multiply 3.6 when converting.
I'll be pissed if the comments are about metric units
- That’s interesting. Obviously, you’d put a center dot to disambiguate millihertz from meter-hertz, but I can’t recall ever having learned a rule about that. So some combinations of units are inherently ambiguous?
  
  Also: Hz/dpt.
  
  Thanks, I hate it
  
  Saw a video using mHz recently and it took way too long to realise the readout was correct and not a typo of MHz ..
  
  ✋ 1 bit
  
  🖖 125 millibytes
  
  Metre hertz? Lol
  
  https://youtu.be/kkfIXUjkYqE
Wait what, jow many kilominutes per hour is one mile per stone?
- African or European swallow?
  
  Unladen or not?
- 3.6
Just multiply by (1000m/1km)(1h/3600s) and cancel out the units, kids
Don't ky/s over unit conversions OP. It's not that hard.
Same order of magnitude, don't bother with the trivial details.
- Is it really tho? log(3.6) ≈ 0.55 so 1 km/h is really closer to 10m/s than 1m/s
It isn't even that much of a time waste you just multiply 1000/3600
- But it would take me a couple of hours to figure that out.
  
  Have you tried converting those hours to seconds?
I hate it when they do it !
The true evil are the fuckers who post recipes in grams instead of cups and ml.
- I don't have time to get out a million little differently sized utensils because I need 2 cups of this, ¼ cup of that, ½ a teaspoon of the third thing etc. when I can put the bowl on a kitchen scale and use the tare function.
- But I love that 😫

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