Re: joules versus newton.meters

["Kilmer, Skip" <kilmers@GREENHILL.ORG>]

Historically, I think Joules are the same as Newton-meters. It makes sense
to me to have the unit of torque be the meter-Newton, which distinguishes it
from the Joule, and gives the correct order for the cross product (not
commutative). Then there is the other possibility, the neuter meetin' which
I suppose is a eunuch convention.
Skip

> -----Original Message-----
> From: Leigh Palmer [SMTP:palmer@SFU.CA]
> Sent: Tuesday, January 30, 2001 2:26 PM
> To:   PHYS-L@lists.nau.edu
> Subject:      Re: joules versus newton.meters
>
> > 1) Left to my own devices, I write torques as netwon.meters;  on
> emotional
> > grounds I prefer newton.meters to joules.
>
> I prefer foot-pounds or inch-pounds for my devices; I don't own a
> torque wrench now, but my old one wasn't SI. On emotional grounds
> I have little feeling for newton meters.
>
> > 2) However, emotions are not physics.  The physics says that if I let a
> > torque of 5 newton.meters act through an angle of 3 radians, I do 15
> joules
> > of work.  Therefore a newton.meter is, in a very physical sense, one
> joule
> > per radian.  Shortening this to one joule is perfectly acceptable.
>
> Yup, perfectly acceptable if you are willing to toss out clarity
> with that hypothetically dimensionless unit. I claim that it has
> substance; one joule per radian means torque in my view, and one
> joule does not.
>
> Leigh