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Re: Simplifying expressions containing units

• To: mathgroup at smc.vnet.net
• Subject: [mg19930] Re: Simplifying expressions containing units
• From: "John M. Jowett" <John.Jowett at cern.ch>
• Date: Wed, 22 Sep 1999 04:11:14 -0400
• Organization: CERN
• References: <7s3pqd$cnn@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

Christian Gudrian wrote:
> 
> Hello!
> 
> Is it possible to simplify the expression
> 
> 4 Newton/2 Kilogram
> 
> to yield Meter/Second^2?
> 
> Mathematica just outputs
> 
> 2 Newton/Kilogram
> 
> Of course it is possible to Convert it using
> 
> Convert[%,Meter/Second^2],
> 
> but that's only possible, if I know, what's coming out at the end of the
> caculation. It would be nice if Mathematica itself would take care of using
> appropriate "versions" of the different derived SI-units.

I think many people have come across this limitation of the standard
Units package that comes with Mathematica (Version 3. at least, I
believe it may be improved for Version 4 but we haven't got that yet).  

We have extended the Units and PhysicalConstants package to produce a
package containing physical constants and units and a few new features
(palette, traditional symbols, a Plot function that deals with units,
...) to fill the gaps.  It was meant for use in particle accelerator
physics but would solve your problem.  Just apply the function
ToFundamentalSI to your expression.  See 

http://wwwslap.cern.ch/~jowett/Accelerator/ConstantsUnits.html

John Jowett


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