Do you use Imperial or Metric? - Page 10

On December 09 2011 16:43 Robinsa wrote:

It doesnt have to do anything with it having the number 10 or not it means it has 10 characters. Namely:
0 1 2 3 4 5 6 7 8 9

Binary for example only has
0 1

so its not base 10 but base 2

On December 09 2011 15:16 Elysian wrote:
One of my friends was discussing this with me before. "Standard" (imperial) is actually a very convenient notation to use in civil engineering. Basically, metric gives you precision and easy scales but at intervals that aren't very useful in a practical sense (e.g. day to day). While both metric and imperial can be broken into fractions, everyday measurements usually are usually *small* whole numbers when done in imperial as opposed to metric.

A few other examples:

Long Distances:
There aren't many times when you use say "go 700 feet that way" or "after 200 meters turn right". If you're in the city, you usually say go X number of blocks. If you're travelling farther distances, you'll want to use kilometers or miles. I think we can all agree that miles and kilometers are about equally useful in that respect.

Short Distances:
If you are trying to point something out to someone in the same room, I don't know what the "standard" increment of measurement is in metric (10 cm?) but increments of a half foot are quite easy to work with and scale well (it's easier to triple 2.5 feet than it is to triple 75 centimeters).

Building material sizes:
Most metal sizes (e.g. rebar, welding, metal sheets) can have precision to 1/8". The equivalent to that in metric is 3.175mm. While you could say "yeah but they could have just made metal in increments of 3mm", imperial has benefits when you start looking at areas and moments of inertia.
Rebar #'s are done in 1/8 of an inch increments; so a #4 rebar has a diameter of 4/8 or 1/2 an inch, #8 rebar has a diameter of 1 inch, #9 has a diameter of 9/8 of an inch. The corresponding mm's are 12.7, 25.4, and 28.65 (you don't use cm that often since stress is often measured in megapascals, N/mm^2). The areas of these rebars are: .2in^2, .44 in^2, and 1 in^2 or 129mm^2, 509mm^2, and 645mm^2; imperial here is much easier to spot check.

Moments of Inertia:
In order to calculate how much a beam will deflect (we have to control deflection in order for people to feel comfortable in a building), you need to use moments of inertia. Moments of inertia have units of length^4. I'm not sure if these are usually done in cm or mm (since no stress is involved) but in either case the metric value comes out to be substantially larger than the standard value. In the case of mm, 78 in^4 becomes 32,466,051 mm^4. In tall buildings, those moments of inertia can quickly rise to billions or trillions for the members at the base.

Scale:
Because you (usually) want to stay in the units of stress, you typically stick with inches or mm all the way through your calculations. You may say, 32466051 mm^4 is no problem, just use .3246 cm^4, but then you have to be very careful whenever you are using powers (for example, in concrete analysis you usually use square roots) since 10mm^(0.5) will not give you the same value as 1cm^(0.5).
Although the inches to feet conversion might sound quite stupid, it offers a check to make sure you haven't forgotten to convert units anywhere since the number itself actually changes (in metric only the magnitude would change).


Anyways, I think that these are a few of the reasons why it has stayed in use for so long. From a science standpoint, I agree that metric would be more useful since it offers scale and a high degree of precision. From an engineering standpoint, however, inches and feet do have their uses.

On December 09 2011 13:32 Keyboard Warrior wrote:
Advantages of Standard
1. Standard goes more naturally with fractions - quarter of a pint, half foot, etc. Technically, you don't say half meter but rather 50 centimeters or 500 millimeters.

2. Standard units are more practical and convenient. No one goes to the grocery to buy 400ml drink, instead, they buy it in 12 ounces. No one buys 5 meters of wood, instead, they buy it is 1x1x12, all in feet.

On December 09 2011 17:06 Simberto wrote:


But he has a point, every b-adic system would be base 10 in its on system.

Binary is base 2 and has 2 digits, or 10 in binary
Dezimal is base 10 and has 10 digits in dezimal
Duodecimal is base 12, has 12 digits, or 10 in duodecimal
Hexadecimal is base 16 and has 16 different digits, or 10 in hexadecimal.

So he is quite right that it would be much more universal to name a system after its highest digit, and not after the first number with two digits in it.