CM

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WHAT IS IT?

This is a project that lets you explore the concept of Center of Mass.

HOW IT WORKS

You start of with a system of mass. The system is divided into two sides with a divider in the middle. The left and right sides are green and blue respectively and are divided into little squares representing mass. In the center of the system is a white dot that represents the location of the Center of Mass of the entire system. As one eliminates blocks, the center of mass changes.

HOW TO USE IT

You can eliminate blocks in one of three ways:

You can eliminate blocks randomly from each side simultaneously.
You can eliminate blocks from one side or the other randomly.
You can eliminate blocks from a specific location by clicking that location with the mouse.

THINGS TO NOTICE

Notice how the center of mass changes as you eliminate blocks. Does it move into the boundary of existing Mass? Does it moved into the empty space vacated by the mass?

THINGS TO TRY

Can you use this model to predict where the center of mass will end up? Can you eliminate mass to make the Center of Mass move to a specific location?

CREDITS AND REFERENCES

Thanks to James Newell for his original model and thanks to Pratim Sengupta for his contributions to making this model work.

For additional information:

Porter, D.A., and Easterling, K.E., Phase Transformations in Metals and Alloys, 2nd ed., Chapman & Hall, 1992

Shewmon, P.G., Diffusion in solids, 2nd ed., TMS, 1989

HOW TO CITE

If you mention this model in an academic publication, we ask that you include these citations for the model itself and for the NetLogo software:

Wilensky, U. (2007). NetLogo Solid Diffusion model. http://ccl.northwestern.edu/netlogo/models/SolidDiffusion. Center for Connected Learning and Computer-Based Modeling, Northwestern University, Evanston, IL.
Wilensky, U. (1999). NetLogo. http://ccl.northwestern.edu/netlogo/. Center for Connected Learning and Computer-Based Modeling, Northwestern University, Evanston, IL.

In other publications, please use:

COPYRIGHT AND LICENSE

CC BY-NC-SA 3.0

This work is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-sa/3.0/ or send a letter to Creative Commons, 559 Nathan Abbott Way, Stanford, California 94305, USA.

Commercial licenses are also available. To inquire about commercial licenses, please contact Uri Wilensky at uri@northwestern.edu.

Comments and Questions

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Click to Run Model

breed [masslets masslet]
breed [cms cm]
breed [killers killer]
masslets-own [mass]

to setup
  clear-all
  set-default-shape MASSLETS "square"
  ;; make green atoms on left
  ask patches with [pxcor < 0]
    [ sprout 1 [ set breed masslets set color green ] ]
  ;; make blue atoms on right
  ask patches with [pxcor > 0]
    [ sprout 1 [ set breed masslets set color blue ] ]
  ;; plot the initial state of the system
 crt 1 
 [
   set breed cms
   set shape "circle"
   set size 1
   set color white
   setxy (mean [xcor] of masslets) (mean [ycor] of masslets)
   ]
 
  reset-ticks
end 

to go
  tick
  ask cms [setxy (mean [xcor] of masslets) (mean [ycor] of masslets)]
  if mouse-down?   
  [ ask masslets with [pxcor >= mouse-xcor - kill-factor and pxcor <= mouse-xcor and pycor >= mouse-ycor - kill-factor and pycor <= mouse-ycor] [ die ]]
  ;; no prey here? oh well
  ifelse cm-view = true [ ask cms [st]][ask cms [ht]]
end     






  
;
;
;; Copyright 2007 Uri Wilensky.
;; See Info tab for full copyright and license.

There is only one version of this model, created about 13 years ago by Pratim Sengupta.

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This model does not have any descendants.

NetLogo

CM