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From: Family Schabel (family_at_[hidden])
Date: 20220829 23:47:47
Hi Bert,
Maybe this link will clarify:
https://physics.stackexchange.com/questions/37881/whyistorquenotmeasuredinjoules
Boost Units explicitly keeps track of angular displacement for this (and similar reasons). The unit of torque really should not be energy (J or N.m) because a torque is a force applied tangentially, so, to compute the amount of energy required to exert a torque one needs to take the product of the force with the angular displacement. The nomenclature is a bit confusing because, as you note, newton_meter is not the same as newton*meter  the convention is that torque is measured in newton meters, but it is really newton meters per radian as encoded in the library. If that werenâ€™t the case, you could equate torque with energy, which is the kind of mistake Boost Units is intended to help prevent.
Matthias
> On Aug 25, 2022, at 5:27 PM, Albert Dvornik via Boost <boost_at_[hidden]> wrote:
>
> It looks like my previous message wasn't visible by nonHTML readers
> (including the list archive) because I didn't configure my socalled
> mailer correctly. Sorry for the duplication and the hassle.
>
> bert
>
> 
> Hi, all.
>
> The definitions of boost::units::torque_dimension,
> boost::units::si::torque, boost::units::si::newton_meter and
> boost::units::si::newton_meters seem broken. The most obvious symptom
> of this is that boost::units::si::newton_meter isn't the same thing as
> boost::units::si::newton * boost::units::si::meter (i.e. an actual N
> m), but is instead defined to be equivalent to *N m / rad* instead.
>
> I'm attaching a source file that shows the problem. I've compiled it
> with Boost 1.80, g++ 10.2.1.
>
> Am I confused in some way? If not, then I believe that the fix would
> be to modify boost/units/physical_dimensions/torque.hpp and remove the
> ", plane_angle_base_dimension,1" in the current definition of
> torque_dimension.
>
> Regards,
> bert Dvornik
>
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