a (metric) unit

Well, my question was a bit more precise than that. I know that objects on moon wieghs 6 times less than on earth. But since Pound is a weight unit, not for mass as in Kg, so my question was whether a pound weight scale will give a correct reading when used on moon. i.e will read 6 times less.

Anyhow, seems I will have to do some memory refreshment to get the answer :-)

Jim, a better idea: instead of wearing goggles, why no you wear a space suit when you cut onions. No crying, it’s guaranteed

A spacesuit: good idea. The pound has been used both as a weight and a mass unit. Scales usually measure the amount of force applied to them so it doesn't matter whether the scale gives kilograms, Newtons, pounds, momme, dynes or cloves. A sixty kilo person would take his scales to the Moon and they'd read ten kilograms or 2 stone one pound. He could then proceed to cut his onions to his heart's content without a tear in sight.

http://en.wikipedia.org/wiki/Pound_%28mass%29

>>A sixty kilo person would take his scales to the Moon and they'd read ten kilograms <<

But you just said his mass is sixty kilos!

Yeah, and his mass doesn't change. He weighs less on the Moon though. Now the scales don't know whether they are on the Earth or the Moon (though it would be easy to design scales which did) so they'd give the wrong reading. The measurement they give is based on the force not the mass. On Earth the scales will detect 588 N which they convert to 60 kg. On the Moon they detect 98 N which they mistakenly convert to 10 kg under the assumption that they are on Earth. These are your regular bathroom scales. If, on the other hand, you use old style balance with a beam and fulcrum (you know, like a see-saw),* then it won't matter which planet or moon you're on they'll still read 60 kg.

* ... like this one http://en.wikipedia.org/wiki/Image:Balance_scale.jpg

**Now the scales don't know whether they are on the Earth or the Moon (though it would be easy to design scales which did) so they'd give the wrong reading.**

Jim: again, I was asking about pound scale only, not kg scale. So I might disagree with you (but I am not very sure if I am correct, or not)


For a 60-kg man, on earth the kg scale reads 60 kg (which is correct). The pound scale reads 132.5 pound (also correct). On Moon, the kg scale will read 10 kg (wrong because the mass has not changed). The pound scale will read 22 pound (correct because pound is a force unit, or weight unit in this case)

So my conclusion is that the pound scale CAN be used on moon to indicate weight…please correct me if I am wrong.

Like he pointed out, only the balance scale would determine the mass accurately. An ordinary scale is dependent on the force of gravity.

"In many contexts, by convention, the term 'pound' refers to a unit of force. However, in other contexts, the 'pound' refers to a unit of mass. In circumstances where there may be ambiguity otherwise, 'pounds-force (lbf)' can be used to refer to the unit of force and 'pounds-mass (lbm)' can be used to refer to the unit of mass."

http://en.wikipedia.org/wiki/Pound-force

So if your scale reads "22 pounds-force" on the Moon then, yes, it would be correct.

The ambiguity comes because the term "pound" is been used both for a unit of mass and a unit of force (and a unit of currency but that's another story). It all depends on context. However, in the context of imperial system a pound is currently defined as 0.453 592 37 kilogram exactly. If you're using the term "pound" as a unit of force, then it's not an imperial pound.

Weights and Measures Act 1963
http://en.wikipedia.org/wiki/Pound_(mass)
http://www.bailii.org/ew/cases/EWHC/Admin/2002/195.html

Thanks Jim.

I think the "pound" which has been refered to for the past few weeks in this thread is the force pound Ibf...just not to confuse the others.

Amazing how much time one can spend on obsolete units.

I shall keep cutting onions as I always did, without any paraphernalia and crying.

<<Uriel, are you American? If so, you should be used to senseless metric quantities. America is metricating by turning USC quantities into grams, ml (silly soft conversion) and alienated even slightly metric inclined people with these useless numbers. Worse still, doing that gave metric ignorants plenty ammunition to point out how idiotic that system is compared to simple fpi. No wonder that metrication never made it in the States.
As to rounded metric numbers, it makes price comparisons so much easier. What is a better price, a 328 g tin of salmon at $ 6.65, or 500 g for $ 9.00? Most people need a calculator to work that out.>>



Yes, I'm American, but I think that rather than trying to hoodwink people, it's just that most products found in the US are sold all over North America, in both Metric countries and imperial ones, so we just go ahead and put both on the can. The "rounder" number is the one that was the original measurement; the odd ones are the equivalents in the other system.
This mass marketing approach is also why many things are also labelled in English, French and Spanish in the US -- so they can be sold in Mexico and Canada as well. (It's also fun to compare the wording and pick out cognates, etc. Or at least, that's what I do in the shower.)

Uriel : « Or at least, that's what I do in the shower ».

C'est à ça qu'on reconnaît les mordus de langues (si j'ose dire...) !

;)

Uriel,

You know, don't you, that you don't use imperial in the US. The imperial system is ever so slightly different to the US one. A US fluid ounce is about a millilitre bigger than an imperial one but since it only takes sixteen of them, as opposed to twenty, to make a US pint the imperial pint is about a decilitre bigger thus six US pints are approximately equal to five imperial ones.

Then, of course, you've got dry gallons in the US too not to mention short tons and long tons. Don't forget the good old Troy ounce. Is it any wonder the world was so quick to adopt the metric system? Well, most of the world.

Those poor Canadians flooded with American beer sold in bottles of twelve US ounces but labelled in millilitres whilst their domestic beer is sold in bottles of twelve imperial ounces again labelled in millilitres ... how confusing it must be. On the other hand, I suppose the bigger US ounce would almost make up for the fact that American beer is so much weaker (so they say).

They could buy their beer by the can, though, and get the best of both worlds. Yes, Canadian beer cans are bigger than Canadian beer bottles ... 14 millilitres bigger. This is the beauty of half-hearted metrication. Better off sticking to plain old hogsheads, barleycorns, scruples and bovates than rounding them all off to the nearest millilitre, micrometre, centigram or are.

Uriel
<<<Yes, I'm American, but I think that rather than trying to hoodwink people, it's just that most products found in the US are sold all over North America, in both Metric countries and imperial ones, so we just go ahead and put both on the can. The "rounder" number is the one that was the original measurement; the odd ones are the equivalents in the other system.
This mass marketing approach is also why many things are also labelled in English, French and Spanish in the US -- so they can be sold in Mexico and Canada as well. (It's also fun to compare the wording and pick out cognates, etc. Or at least, that's what I do in the shower.) >>>

No Uriel, it is more complicated than that. The European Union is not interested in having useless USC quantities on imported cans and bottles. It gave the US already one extention of 10 years to introduce metric labelling only on goods exported to the EU. This extention runs out on the 31.12.2009. EU laws are much more user friendly than US laws, which means labels are already cluttered with different languages. So why compound that to the detriment of buyers with more useless information? It might be fun for you, but not for busy European housewives. Besides, it costs consumers extra money for nothing.

***It gave the US already one extention of 10 years to introduce metric labelling only on goods exported to the EU***

Surely the solution is simple.....the EU stops importing goods from the insular Americans. End of.

My mother has a friend who has a sister living in California USA and occasionally she sends stuff over from there and the goods have imperial labels..... with the metric equivalents in brackets! She also sends recipes which Dolly hasn't a hope in hell of understanding. I don't think it's any use the EU expecting the Americans to comply with any stipulation from outside their own borders whatever the issue......the British have traditionally been conservative in the past, but never on a par with the current American version.

You're right about the multi lingual situation in the EU whatever it is you buy. Take any electrical/electronic device for example........the instruction leaflets are pages long with the full directions and information given in each individual Language. It takes a wee while to look for the section headed "GB"...with everything written in English. :-)

Jim, you're right. And what the hell is a tonne, compared to a ton? Have to admit that I've never heard of "hogsheads, barleycorns, scruples and bovates", though....

eric, like I said, those measurements are primarily for sales within the Americas, primarily, not for export to the EU. I would imagine that such exports are labelled differently.

A lot of times it depends on the type of product, also. I was thinking of household products, which are often in some combination of English, French, and/or Spanish, but on medical supplies I often see many more languages -- lots of European ones plus Chinese, Japanese, and occasionally other Asian languages.

Damian, one of the funniest things I've heard in relation to recipes not quite making it across the pond was a story where an Englishwoman acosted an American and demanded to a translation for half-and-half in a recipe that an American friend had once sent her -- "Now, half of wot an' half of wot?" (Half-and-half is an equal mixture of milk and cream, available in the dairy case at any American supermarket. I'm sure it exists elsewhere as well, just under a different name.)

I myself have a British cookbook. Most of the measurements I can figure out, although I'm not used to quantities being given in weights (other than say, half a pound of butter or something like that), but some of the ingredients are called by different names, and some of the cooking techniques are as well -- thank god for photographs! So the confusion cuts both ways.