       Re: Mathematica 9--Is This A Joke?

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• Subject: [mg128866] Re: Mathematica 9--Is This A Joke?
• From: "djmpark" <djmpark at comcast.net>
• Date: Sat, 1 Dec 2012 04:34:10 -0500 (EST)
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```Kevin,

I think the Units package is still there, but just not listed in the
Standard Extra Packages.

The items that were in PhysicalConstants are now symbols in regular
Mathematica.

My personal opinion is that it is not very good practice to include units in
equations at the first step. It is better to keep all the equations strictly
symbolic, do whatever kind of solving or manipulation you have to do, and
then at the end substitute values and units to obtain specific answers.

David Park
djmpark at comcast.net
http://home.comcast.net/~djmpark/index.html

From: Kevin Wheelock [mailto:jiyajbe at gmail.com]

I just installed Mathematica 9. I am horrified. How did this get past QA and
Usability Testing?

Example: Newton's 2nd Law

In Mathematica 8:

In:= Needs["Units`"]

In:= M := 5 Kilogram

In:= a := 10 Meter/Second^2

In:= F := M a; F

Out= (50 Kilogram Meter)/Second^2

In:= Convert[%, Newton]

Out= 50 Newton

In Mathematica 9:

In:= M := Quantity[5, "kg"]

In:= a := Quantity[10, "m/s^2"]

In:= F := M a; F

Out= 50kg m/(s)^2

{At this point, Mathematica pops up a dialog offering, among other things,
to let me convert this unit. Okay, I enter "N" in the field I was presented}

In:= UnitConvert[
Quantity[50, ("Kilograms" "Meters")/("Seconds")^2], "N"]

During evaluation of In:= UnitConvert::unkunit: Unable to interpret unit
specification N. >>

Out= UnitConvert[50kg m/(s)^2,N]

{Huh. Okay, I try other things...}

In:= UnitConvert[
Quantity[50, ("Kilograms" "Meters")/("Seconds")^2], N]

During evaluation of In:= UnitConvert::unkunit: Unable to interpret unit
specification N. >>

Out= UnitConvert[50kg m/(s)^2,N]

In:= UnitConvert[
Quantity[50, ("Kilograms" "Meters")/("Seconds")^2], "Newton"]

During evaluation of In:= UnitConvert::unkunit: Unable to interpret unit
specification Newton. >>

Out= UnitConvert[50kg m/(s)^2,Newton]

In:= UnitConvert[
Quantity[50, ("Kilograms" "Meters")/("Seconds")^2], "Newtons"]

Out= 50N

{Ha! I finally guessed right!}

Who the HELL thinks this is better????? "M := Quantity[5,"kg"]"??? Are you
KIDDING ME????

Give me back version 8, and QUICKLY!

```

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