Scrap car battery.

[Roger Hayter]

ISTR a thing called a poundal. I won't look it up, because that would only spoil it.

[Robin]

Others might consider its use as a unit of weight in UK and EU legislation pretty formal.

[Fredxx]

Which just goes to show how clueless law writers and their teachers are.

The problem is historic, where pounds was also considered a weight by those less well informed.

[Robin]

Then please share your suggestion for practicable definitions of weights for the purposes of "weights and measures" legislation which don't equate it with mass. And FTAOD that's practicable including taking account of the variation in gravitational acceleration from place to place.

[Fredxx]

Simply by describing objects measured by way of by mass and not weight. We have volumes measure in unit of pints or litres, so why not measure mass in terms of units for 'mass'?

[Robin]

Three points on that.

First, that is not defining weight at all.

Second, it makes me wonder if you know the UK legislation - especially:

"for the purposes of any measurement of weight falling to be so made, the weight of any thing may be expressed, by reference to the units of measurement set out in Part V of that Schedule, in the same terms as its mass." (s.1(2) Weights and Measures Act 1985)

Third, "law writers" legislate with more than an eye to people going about their daily lives, and so wish to avoid such things as:

Customer: "How much does that leg of pork weigh?" Butcher: "I can't tell you that. I can tell you it's mass is 1.2 kg."

[Robert]

Doesnt it depend on what type of "scales" he uses ?

[Max Demian]

Depends on how you are measuring it. Traditional scales with the load one side and weights the other, or with a sliding weight, measure mass. (Beam balances) Spring or electronic scales measure weight.

My electronic kitchen scales are calibrated in grams or pounds and ounces. Perhaps they should also have Centinewtons (cN), but, since 1 cN = 1.02 grams-force, it wouldn't make much difference to cooking.

[Robert]

My Applied Maths learning spanned the transition from imperial to SI units (with cgs thrown in) . It took me a long time to work out where or if I needed a "G" in the equation. Seemed so obvious once we were just using SI units.

[Robin]

<snip>

I think all kinds of "scales" could cope after the butcher's been told how "weight" is defined for traders. Not just the units (presumably Newtons) but also what value of "g" is to be used for balances (or for calibration). I don't know how much it varies across the UK but I bet the SNP would soon find out ;)