On Tue, 20 Nov 2018 at 07:06, Steven Watanabe via Boost-users <boost-users@lists.boost.org> wrote:
This is not the unit you want.  The SI
unit of force is N, not kg. 

One wonders what has happened to the school system these days, this is basic stuff that was taught to kids 13/14 years of age ad nauseam.

To expand on what Steven has been [economically] stating: Wikipedia definition: One newton is the force needed to accelerate one kilogram of mass at the rate of one metre per second squared in the direction of the applied force. And from Wikipedia again: ... an object with a mass of 1.0 kilogram will weigh approximately 9.81 newtons on the surface of the Earth (its mass multiplied by the gravitational field strength), since the newton is a unit of force, while the kilogram is a unit of mass.

kilogram-force
is not currently provided by Boost.Units
and you'll need to define it yourself.

From Wikipedia: Kilogram-force is a non-standard unit and is classified in SI Metric System as a unit that is unacceptable for use with SI. It is equal to the magnitude of the force exerted on one kilogram of mass in a 9.80665 m/s2 gravitational field (standard gravity, a conventional value approximating the average magnitude of gravity on Earth). Therefore, one kilogram-force is by definition equal to 9.80665 N. The "by definition" here is important, depending on where you are on the planet, the real value will vary.

In the meanwhile the Kg has been redefined. The new definition is based on invariant constants of nature. Is there anything Boost needs to do to comply with this new definition [or does it require serious multi-precision to actually see a difference [I suspect so, but still it should be defined in terms of these constants]]? The constant that did get redefined to make this [the above Kg definition] possible is the Planck constant.

The new value [as of 20 May 2019] of the Planck constant by the ISO standard is set to 6.626 070 150 x 10-34 J⋅s. Some other constants got redefined as well: ... in order to support the redefinition of the SI base units, CODATA made a special release that was published in October 2017.[30] It incorporates all data up to 1 July 2017 and determines the final numerical values of the Planck constant, h, Elementary charge, e, Boltzmann constant, k, and Avogadro constant, NA, that are to be used for the new SI definitions.

degski
--
“If something cannot go on forever, it will stop" - Herbert Stein