Gents
Not to open old wounds, but I think I have an explanation as to why
kilograms (mass) are used as units of weight rather than Newtons.
I think the reason is because, as our elucidated bretheren pointed out,
mass is constant (at least for our purposes. I do not intend to hang
around any black holes).
I am on earth. I buy a small packet of rice weighing x Newtons - it
fits
in my store cupboard. The following day I set off for a self catering
holiday in the Moon. On arrival I fancy a chilli and rice. I go to the
local store and ask for x Newtons of rice as per usual. The
store-keeper
gives me an odd look and says sure, he'll deliver it. 'How kind' I
think.
On returning to my holiday appartment I find it awash with rice. I am
going to have to eat an awful lot of chilli before I can go to bed! (Nb
this is exaggerated for illustrative purposes)
If I had purchased the kilogramme equivalent of x Newtons on earth, and
subsequently asked for the same number of kilos of rice in the moon I
would
have received a packet of rice the same size as the one obtained on
earth.
The weighing machine would have to be calibrated or have a conversion
factor to take account of the moon's gravity.
You could, of course do it the other way round mathematically but that
would then involve making the mass variable and the weight constant
dependent on location in the solar system. My asbestos underpants get
scorched enough on model RR pages with out adding the world community of
physicists to the chase! ;-o
Sam Evans in the UK
