Re: weight vs. mass
- S potesenim zjistuji, ze veda je na celem svete stejna.
--- In Czechlist@y..., "Rachel Thompson" <rachel.thompson@s...> wrote:
> > I have a vague recollection from high school chemistry class that
> > actually is a scientific distinction between "mass" and "weight"
> Yes, of course, as Simon already explained:
> "To answer the mass-vs-weight query, I was always taught that,
> strictly speaking, mass is measured in grammes whereas weight (being
> a force) is measured in Newtons. A man on the moon, for example,
> weighs much less than on earth, but his mass is the same regardless
> of location (relativistic considerations aside)."
> > For convenience, the "mass" of any particular body is generally
> > in the same terms as the "weight" that same body has when here on
> earth, at
> > sea level.
> Actually, what we think of as "weight" is actually mass, not the
> way round. 1kg is a mass, not a weight. A 1kg object has 1kg of
> "stuff" in it, and will always have the same amount of "stuff"
> it, even if it is floating "weightless" in orbit. On earth, 1kg
> "weighs" 10N. This means it "pushes down" on the earth with a
> 10 Newtons. But in different conditions it could weigh something
> completely different.
> > And, indeed, I suspect that in many contexts this entire
> > distinction is completely irrelevant.
> Yes, of course, in everyday contexts it is irrelevant. However, in
> scientific text (which was what we were discussing), it is more
> important to retain the distinction. It could actually be argued
> was quite persuasively by my Physics teacher at school) that it's
> trying to make the distinction in everyday speech as well, in order
> help children to understand the totally different concepts
> the scientific definitions (since children often find them extremely
> difficult to grasp). I don't know that I'd go that far, because it
> seems to me that weight is so much a part of everyday speech, but I
> think it's important not to dismiss the distinction in a scientific