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Re: Mathematica 9--Is This A Joke?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg128870] Re: Mathematica 9--Is This A Joke?
  • From: Murray Eisenberg <murray at math.umass.edu>
  • Date: Sat, 1 Dec 2012 04:35:30 -0500 (EST)
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  • References: <20121130105725.8B47768B0@smc.vnet.net>

No need to be "horrified". Just read the docs!

Yes, there's not "Newton". But did you notice that "Kilograms", 
"Meters", and "Seconds" are all plural. So is "Newtons"!

This is easy to discover: Use the Control + = special input form for 
calling Wolfram|Alpha with input

  1 Newton

(You'll get result 1 N.) But then put //InputForm on the cell and 
evaluate again. You'll get:

  Quantity[1, "Newtons"]


On Nov 30, 2012, at 5:57 AM, Kevin Wheelock <jiyajbe at gmail.com> wrote:

> 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[1]:= Needs["Units`"]
>
> In[2]:= M := 5 Kilogram
>
> In[3]:= a := 10 Meter/Second^2
>
> In[4]:= F := M a; F
>
> Out[4]= (50 Kilogram Meter)/Second^2
>
> In[5]:= Convert[%, Newton]
>
> Out[5]= 50 Newton
>
>
>
> In Mathematica 9:
>
> In[1]:= M := Quantity[5, "kg"]
>
> In[2]:= a := Quantity[10, "m/s^2"]
>
> In[3]:= F := M a; F
>
> Out[3]= 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[4]:= UnitConvert[
> Quantity[50, ("Kilograms" "Meters")/("Seconds")^2], "N"]
>
> During evaluation of In[4]:= UnitConvert::unkunit: Unable to 
interpret unit specification N. >>
>
> Out[4]= UnitConvert[50kg m/(s)^2,N]
>
> {Huh. Okay, I try other things...}
>
> In[5]:= UnitConvert[
> Quantity[50, ("Kilograms" "Meters")/("Seconds")^2], N]
>
> During evaluation of In[5]:= UnitConvert::unkunit: Unable to 
interpret unit specification N. >>
>
> Out[5]= UnitConvert[50kg m/(s)^2,N]
>
> In[7]:= UnitConvert[
> Quantity[50, ("Kilograms" "Meters")/("Seconds")^2], "Newton"]
>
> During evaluation of In[7]:= UnitConvert::unkunit: Unable to 
interpret unit specification Newton. >>
>
> Out[7]= UnitConvert[50kg m/(s)^2,Newton]
>
> In[8]:= UnitConvert[
> Quantity[50, ("Kilograms" "Meters")/("Seconds")^2], "Newtons"]
>
> Out[8]= 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!

---
Murray Eisenberg                                    
murray at math.umass.edu
Mathematics & Statistics Dept.      
Lederle Graduate Research Tower            phone 413 549-1020 (H)
University of Massachusetts                               413 545-2838 (W)
710 North Pleasant Street                         fax   413 545-1801
Amherst, MA 01003-9305








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