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Unit conventions (SI versus others)

  1. Feb 3, 2017 #1
    Can anyone explain to me how it comes that US not have accepted the use of SI ?
    Do you not understand the benefits ?

    Would it not be more effective if the new generation of students could concentrate on understanding fundamental physics relations rather than struggle whith old-fashioned and confusing unit transformations ?

    As far as I know it is only US beside Liberia and Burma who has not understod the importance of this.
    Why ?
     
  2. jcsd
  3. Feb 3, 2017 #2

    Choppy

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  4. Feb 3, 2017 #3

    Student100

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    Struggle with confusing unit transformations? I don't think I ever had a physics class that didn't use SI, except the odd course that used Gaussian units. Certainty, no course ever asked me to convert foot pounds to newton meters if that's what you mean.

    So we do use SI primarily in science courses, and not Imperial units in the US.
     
  5. Feb 3, 2017 #4

    Vanadium 50

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    But the US has been metric since 1866!
     
  6. Feb 3, 2017 #5

    Student100

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  7. Feb 3, 2017 #6

    Dale

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    I don't understand the benefits. Scientists and engineers are already free to use SI if they want, and so are manufacturers. So what are the benefits?
     
  8. Feb 4, 2017 #7

    Ibix

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    Thank you for that.
    "YARDS! What happened to CUBITS!?"
    :biggrin:
     
  9. Feb 4, 2017 #8

    jbriggs444

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    It would be nice not to have fifty bajillion sizes of sockets in my set.
     
  10. Feb 4, 2017 #9

    Dale

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    So auto mechanics could reduce the cost of their tools. That would be a benefit to them, but tool manufacturers would lose sales so that would be a disadvantage to them.
     
  11. Feb 4, 2017 #10

    jbriggs444

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    Although you can run an economy by paying one batch of people to make holes and another batch of people to fill them in and while both groups of people will consider this to be to their benefit, there are better options.
     
  12. Feb 4, 2017 #11

    Vanadium 50

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    Run? I thought you said "ruin". :woot:
     
  13. Feb 4, 2017 #12

    256bits

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  14. Feb 4, 2017 #13

    russ_watters

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    Inertia.
     
  15. Feb 4, 2017 #14

    fresh_42

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    Would be interesting to know, where Joule is actually used instead of calories. I mean, they don't get even this right, as usually all talk about cal and mean kcal. And I can't remember a correct weather report. I usually don't get understood very well, if I complain about temperatures above 300. But °C is SI you could argue. Well, that's right, although not logical, but e.g. °mC isn't allowed here. I vote for Delisle!

    P.s.: I counted 89 (sic!) different miles on the Wiki page!
     
  16. Feb 4, 2017 #15

    Mark44

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    Maybe you would like to volunteer to come here (U.S.) and change all of the millions of property descriptions, all of which are relative to some township (36 square miles), and one or more sections (1 square mile = 640 acres) within the township.

    Here is an example property description for a place in the state of Florida. Care to take a crack at this one?

    metes-and-bounds[1].png
     
  17. Feb 4, 2017 #16

    Astronuc

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    We have the benefit of hybrid units, e.g., kW/ft (linear power) and cal/g (specific enthalpy/energy), in one particular industry. Most of my reports have incorporated both units since they were used in the US, Europe and Asia. I much prefer SI/mks, or mixed units, e.g., W/cm.
     
  18. Feb 4, 2017 #17

    OCR

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    Well, at least that description didn't use chains...

    Although, mostly related to wildland fires, the LMAs still do, to a certain extent...[COLOR=#black].[/COLOR] :oldeyes:

    And then... there's also the good old DBH measurement... so if you want somebody to cruise your timber for a sale, try to find a real short person ... lol

    I'm not even going to talk about log scaling, and the Scribner Decimal C rule...[COLOR=#black].[/COLOR]:oldgrumpy:
     
    Last edited: Feb 4, 2017
  19. Feb 4, 2017 #18
    The drawback to the number 10, the basis of the metric system, is its lack of divisors. No one is complaining about a 24 hour day. One could invent a 10-part year, but then you'd lose the 4 seasons. Many things come in 12's. Some things come in 20's. When something is not metric, there's usually a very pragmatic reason to prefer that system of measure. I like inches and feet, also quarts and gallons. I hope they are not abolished.
     
  20. Feb 4, 2017 #19

    Astronuc

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    Except most engineering applications, particularly in manufacturing, use decimals even when using inches.

    Using divisions like 1/16 inch or 1/32 inch might work for construction, or something similar, but it doesn't work well in precision engineering and manufacturing. When it comes to small parts, we often use mils, or fractions of mils, and sometimes micro-inches.
     
  21. Feb 5, 2017 #20

    Ibix

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    Tenths are convenient because we use base ten because we have ten fingers. I always said we ought to have evolved an extra finger.
     
  22. Feb 5, 2017 #21

    fresh_42

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    A penny for your thoughts! The Sumerians used the base 60 ...:biggrin:
     
  23. Feb 9, 2017 #22
    I know SI is in use in U.S as well as other units are common everywhere
    As a step on the way you can use both old units and SI (as for "cal" and "J" on all food declarations in sweden)
    My point is that physics is hard enough to understand without unit conversions.
    I had a student some years back who went to U.S. For one year between the ordinary in Sweden (17-18 years old)
    He was advised not to study physics because it was considered very difficult, but did so anyway because he liked it.
    I asked how he had done when he was back.
    "The physics was realy easy", he said, "nothing new but all the conversions. But I just converted the given data to SI, solved the problem and gave the answer in the unit that was asked for. Nobody understod how I did, not even the teacher."

    The benefits with SI is simply that physics (and offcourse all technical use of it) will be easier.
     
  24. Feb 9, 2017 #23

    Student100

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    Again, no proper physics course in the US is using anything but SI or other metric type units.

    At most there may be problems given in one set of units and you're asked to convet to SI, but thats only normally in the very beginning when students are learning conversions of all sorts.

    I don't know where your student went, but it isn't normal. Also any physics teacher should be able to convert any type of units and understand unit conversions.
     
  25. Feb 10, 2017 #24
    Yes, and the US Bureau of Standards redefined "customary" units in terms of metric standards. One inch is defined as exactly 2.54 cm. Congress allowed customary units to be used, probably thinking for the time being, but meaning metric units would never be used if it could possibly be avoided.
     
    Last edited: Feb 10, 2017
  26. Feb 10, 2017 #25

    vela

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    What's the big deal? Unit conversions aren't difficult. They're annoying and, at times, tedious, but they're hardly difficult. And as others have pointed out, physics courses typically use SI units.



    I don't believe this for a second.
     
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