[SciPy-User] Error in constants documentation?
Wed Apr 7 12:02:49 CDT 2010
Am Dienstag, 6. April 2010 22:08:53 schrieb Arthur M. Greene:
> It would seem that there is some confusion, in the
> constants.html, between force and mass...
Beside the wrong unit which is fixed now I don't see any confusion.
> Strictly speaking, kg is a unit of mass, Newton a unit
> of force. Weight is force, not mass: A gold brick
> floating in interstellar space is weightless but still
> massive. Pounds and kilograms can be equated, but only
> in some specified gravitational field (like at the
> surface of the earth, where we usually weigh things).
This is true for pounds-force and kilograms. Pounds-mass and kilograms could be equated in any context. Pound itself is ambigous.
> So mass is the more fundamental quantity, since it does
> not depend on gravity for its value. In Imperial units
> (feet, pounds) the unit of mass is the slug:
> http://en.wikipedia.org/wiki/Slug_(mass). This is
> absent from the constants page.
Mmmh.. never heard of it though I read quite some English language aerospace engineering literature. However I'm using SI units. I think pounds-mass is more widely used as a imperial unit of mass.
> Warren Weckesser wrote:
> > Florian Lindner wrote:
> >> Hello,
> >> http://docs.scipy.org/doc/scipy-0.7.x/reference/constants.html chapter Force says:
> >> dyn one dyne in watts
> >> lbf one pound force in watts
> >> kgf one kilogram force in watts
> >> doesn't the watts actually have to newtons as the unit of force?
> > There is a ticket with the same question here:
> > http://projects.scipy.org/scipy/ticket/1001
> > Warren
> >> Regards,
> >> Florian
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