Oh god, you’re bringing back the nightmares of my Heat Transfer final. Our text & most homework assignments were given in an odd mishmash of SI and non-SI units. Final answers up to that point were required to be in SI units so we’d just convert the questions & relevant values from Perry’s, the text, etc and were good to go.
On our final exam all questions, references and required answer format were all (different from the coursework) non-SI units. I figured that rather than convert everything to familiar SI, work out the problem, then convert the answer I’d work in the given units and only convert when absolutely required. Halfway through the time I’m only 1/3 of the way through the questions, panicking, and getting obviously-wrong results so I switch to working in SI and finish just in time. It was not my best mark in university.
Moral of the story: the ugly kludge of various non-SI systems might work okay for simple day-to-day stuff but they blow for anything even slightly complicated. And there’s a tonne of legacy data/equipment out there that uses it
I have converted most of our household weights and measures to metric. I got most of the gear through eBay. Here’s what I recommend:
[ul]
[li]Thermostat - I did find a bell-type mercury switch thermostat in celsius, but ultimately I just bought and installed a digital one. Comfortable room temperature is about 20 degrees.[/li][li]Thermometer - Temperature is a thing people often find tricky to get used to. They know about what 80 degrees feels like. Don’t try to convert. Just get a thermometer with just celsius on it and hang it outside. My wife and I just set our car’s thermometer to celsius and everyday when we went to work we would try to guess the temperature on the way to the car, and then when we turned the car on we’d see who got the closest.[/li][li]Medical Thermometer - I have a digital one, and I wrote the important temperature ranges on the hard plastic case. These are pretty easy to learn – the weird numbers you get in Frigginheit are actually converted from round numbers in celsius.[/li][li]Cooking Thermometer - Since my oven is not ready to be replaced anytime soon, I still use the temperature, though my probe thermometer is set to celsius, and is pre-programmed with the temperature ranges for meats at various levels of done-ness.[/li][li]Measuring Cups/Spoons - I have spoons and cups with only metric measures. If a recipe calls for a teaspoon, I use 5 ml. For a tablespoon I use 15 m. I don’t do much baking, where I’m told proportions need to be more precise, but I generally find 250 ml works wherever you need a ‘cup’.[/li][li]Weight - You want a digital scale anyway. And, since most water-based liquids used in the kitchen are close enough to the density of water not to make a big difference, your tare scale can double as a measuring cup – 1 gram is 1 ml. We also have a digital scale for weighing people. For a recipe that calls for a pound of ground beef, for example, use half a kilo.[/li][li]Distance - You’ll want a meter stick and a tape measure in only metric – you want to be able to read from either side of the thing, and if it’s mixed units, the metric will be on the less convenient side to use. You’ll probably also want a tailor-style measuring tape. Remember that a yard is about a meter long. A standard CD is 12 cm across and 5 cm from the edge to the hole – the hole itself is 2 cm in diameter.[/li][li]Tire Pressure - Again, digital is your friend. My car owner’s manual specifies optimal pressure in kPa, so one of those PSI dealies wouldn’t help me.[/li][/ul]
I’m sure I’m forgetting something it would be handy to let you know. I’ll give it some thought.
Metric is easier for things I have learnt later in life but I still think that soemthing weighs 10 pounds, 22mpg or is 6’2" tall. Metric is better when figuring things out. I love metric.
OK, you got me on that one. What is this thing that weighs 10 pounds, is 6’2" tall and has a fuel efficiency of 22 mpg? Some early penny-farthing bicycle with a motor?
My usual technique in dealing with non-metric units in school assignments is to convert to metric, solve, and then convert back to whatever they want the answer in. I find it rather convenient to be able to derive units as I go as well, which I have much more trouble doing in non-metric systems.
A thought I had a few days ago… Most of the world gives americans shit for being monolingual. I realized we can give you shit for being mono-measuring-systemal.
Get some culture! Expand your horizons! Weigh yourself in pounds every once in a while!
This is why misconfigured printer drivers in the UK often cause the printer to say ‘Load Letter’ (the document was sent as letter size, but the printer only has A4, and wants you to load some Letter-sized paper)
I think that in the US, the most important thing about dimensionless numbers is that they don’t keep changing depending on which custom is in use in the conversation.
Though, things could be worse. In spectroscopy, people customarily use inverse centimeters, and graph them increasing right to left. I still find references that say this is the smart thing to do because the values are more reasonable this way.
I know that this thread is a little old now, but I thought I’d chip in (again) with an example here.
I’m at work at the moment and I’m aiming to produce a script that automates a lot of the hand calculations that had been performed previously. I’m doing all the work in SI units and enabling conversion to other at the end (pilots still think in knots, and older engineers are comfortable visualising feet).
The author of a big document I’m working from has some funny numbers, and working through it it’s clear that they’ve gone straight from using slugs to pounds without converting. According to google 1 slugs = 32.1740486 pounds, so I’m not surprised they didn’t have that one memorised. Obviously, it’s made a big difference and I’ve got a feeling that it’s meant something that I’m working on is heavily over-engineered because they’re expecting the air to be 32x denser.
In fact, delving further into the work that’s been done; it’s clear that they’ve confused pounds (mass) and pounds (force). Which has led them to give the units of pressure as lbs/ft^2 (mass per unit area?) and converted them to Kg (sic)/m^2, which doesn’t make too much sense.
eta: the ‘sic’ bit. I try not to use sloppy prefixes in my own work
I just did some quick-and-dirty ballparking for a typical white sauce recipe usually given in US units in terms of tablespoons of butter and flour per cup of liquid. What would the rule be if you’re cooking in metric?
Some preliminary Googlation seems to suggest that flour is about half as dense as butter. Sauce recipes suggest a 1:1 flour-to-butter ratio by volume, though the amount of flour is really the key determinant of the final sauce – you need enough butter to cook the sauce in. Still, if the density is 1:2, then I find the following rough equivalents to the typical recipes:
Thin: x g Flour, 2x g butter, 30x ml liquid
Medium: x g Flour, 2x g butter, 15x ml liquid
Thick: x g Flour, 2x g butter, 10x ml liquid
I haven’t tried out these ratios yet, but this is in the same ballpark as the standard ratios given, only now in ratios convenient in the metric system. If you don’t have a digital scale, you can use this equivalent for the 15 ml measuring spoons you get in a metric set and the ‘tablespoon’ notches on your butter stick wrapper (1 TB = 14.79 ml, close enough). And depending on what subunits your measuring cup is marked to, you may wish to round up or down on the liquid portion:
Thin: 15 ml Flour, 1 notch butter, 225-250 ml liquid
Medium: 20 ml Flour, 2 notches butter, 225-250 ml liquid
Thick: 30 ml Flour, 3 notches butter, 225-250 ml liquid
