NTNUJAVA Virtual Physics Laboratory
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Author Topic: Blocks and center of gravity  (Read 133464 times)
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Fu-Kwun Hwang
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on: January 29, 2004, 05:31:05 pm » posted from:,,Satellite Provider

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This is a home work problem shown in many Fundamental Physics textbooks .

  • How to stack four uniform blocks on top of a table,

  • so that they extend as far right as possible and still remain stable.

  • How should each be positioned?

  • Can the top block have its entire length beyond the edge of the table.

  • Would you like to play!




  • Rules :

  • So long as the center of gravity is directly above some point

    within area of support, the system will be stable




    1. You can drag and move blocks horizontal with your mouse.

    2. The stability of the sub-system is color coded

      1. Green: the sub-system is in stable equilibrium

      2. yellow: the center of gravity is right above the edge of the supporting block.

      3. red: the sub-system is unstable, it will fall in real life.

    3. The center of gravity for each block is shown as a small blue dot.

    4. If you press "Show c.g." button

      1. The center of gravity for the blocks being moved will be shown as a small circle.

      2. The length of the arrow is proportional to the gravitational force for each balanced sub-system.

      3. Label of this button change to "Hide c.g", and you know what it means.

    5. Current mouse position is shown in the "Text Field" (relative to top left edge of the table)

    6. The percentage to the max. distance is shown on right edge of top block. It will smile when you get 100%

    7. All the other numbers are coordinates measured from the left edge of the current window and they are all color coded.




    8. The left edge of each block under the number
      The center of gravity of each block the number is in
      The center of gravity for all the blocks above the number




    How to make it better? Do I need to make blocks falling down if it is unstable?

    Will it help the students learn more about the concept of center of gravity ?
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    Registed user can get files related to this applet for offline access.
    Problem viewing java?Add http://www.phy.ntnu.edu.tw/ to exception site list
    If java program did not show up, please download and install latest Java RUN TIME
    There are 6 translations,
    Higher number at the end means more translation been done.
    or
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    Fu-Kwun Hwang
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    Reply #1 on: March 30, 2005, 03:51:47 pm »

    New version

    -*-

    Embed a running copy of this simulation

    Embed a running copy link(show simulation in a popuped window)
    Full screen applet or Problem viewing java?Add http://www.phy.ntnu.edu.tw/ to exception site list
    Press the Alt key and the left mouse button to drag the applet off the browser and onto the desktop. This work is licensed under a Creative Commons Attribution 2.5 Taiwan License
    • Please feel free to post your ideas about how to use the simulation for better teaching and learning.
    • Post questions to be asked to help students to think, to explore.
    • Upload worksheets as attached files to share with more users.
    Let's work together. We can help more users understand physics conceptually and enjoy the fun of learning physics!
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    j142
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    Reply #2 on: January 23, 2009, 01:37:31 pm »

    There is a problem with this simulation.

    If i drop the topmost block then still other block's C.G are in right side

    I mean to say if i drop the top box then other block's C.G. should again come in center, because now dropped box is not a part of the system.

    jignesh
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    Fu-Kwun Hwang
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    Reply #3 on: January 23, 2009, 01:52:16 pm »

    What you ask for is another problem.
    The above simulation (in first message) calculated  center of mass for
    1. the top block
    2. two blocks from the top
    3. three blocks from the top
    and  all four blocks.
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    j142
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    Reply #4 on: January 23, 2009, 01:56:57 pm »

    Ok

    Thank you

    Very nice simulation.
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    jiaen
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    Reply #5 on: April 09, 2009, 02:30:03 am »

    Thank you for this nice applet.  Smiley

    I have used it in one of my lesson construction. here is the link

    http://mynielife.pbwiki.com/simulation-lesson

    I'm a teacher-in-training, it will be wonderful if anyone can make some suggestions as to how i can improve and build upon it.
    Thank you again!
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    yimseo
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    Reply #6 on: May 08, 2010, 09:18:58 pm » posted from:Singapore,,Singapore

    Sorry, But i can't view the simulation how?
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    jenny.smith
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    Reply #7 on: July 23, 2010, 08:00:48 pm » posted from:Mumbai,Maharashtra,India

    @Fu-Kwun Hwang just gone through your explanation regarding the blocks and center of gravity its so simple that i can understand deeply.Great work by you.
    « Last Edit: July 23, 2010, 08:11:02 pm by jenny.smith » Logged
    anntaylor
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    Reply #8 on: September 16, 2010, 06:41:34 pm » posted from:Karachi,Sindh,Pakistan

    I think it has some error it can't simulate for me.
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    lookang
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    http://weelookang.blogspot.com


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    Reply #9 on: September 16, 2010, 06:59:30 pm »

    using windows xp
    java update 20
    Firefox 3.6.10
    work fine for me
    see the picture i just captured.

    i did experience some problem on web deployed java applet using java update21 with Firefox older version 3.6.9. sometimes can, sometimes cannot show


    * blockandcgejs.png (8.23 KB, 503x316 - viewed 258 times.)

    * blocksandcgjdk.png (4.64 KB, 302x303 - viewed 253 times.)
    « Last Edit: September 16, 2010, 07:01:45 pm by lookang » Logged
    ahmedelshfie
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    Reply #10 on: September 16, 2010, 07:09:46 pm » posted from:SAO PAULO,SAO PAULO,BRAZIL

    anntaylor as like porf lookang explain in him answer you can do one thing more
    Restor PC and try access again sometimes have errors with java and communicate Page.
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    kddesigns247@yahoo.com
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    Reply #11 on: September 18, 2010, 07:21:33 am » posted from:Marietta,Georgia,United States

    Tried to copy paste did not work, please let me know have a MAC computer anyone know?
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    Fu-Kwun Hwang
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    Reply #12 on: September 18, 2010, 08:11:08 am » posted from:,,Taiwan

    Try to download file, unzip it and open html file with your browser to view it.
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    anntaylor
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    Reply #13 on: December 21, 2010, 05:55:29 pm » posted from:Karachi,Sindh,Pakistan

    zip folder is not opening and showing corrupt file error
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    Fu-Kwun Hwang
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    Reply #14 on: December 21, 2010, 06:09:54 pm » posted from:Taipei,T'ai-pei,Taiwan

    I just download the file again. It seems working properly.
    You might want to try to download it again. (Close the browser first and re-open it).
    Otherwise, you will only get cached file.
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    anntaylor
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    Reply #15 on: December 22, 2010, 04:28:30 pm » posted from:Karachi,Sindh,Pakistan

    Thanks, Yes now its working I think first download file is not completed.


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    jt11347
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    Reply #16 on: January 13, 2011, 10:57:02 am » posted from:Houston,Texas,United States

    how do i run the simulations?? I am having trouble running them. I'm a complete noob with java. I downloaded ejs but I cant figure out how to run all these simulations.

    Thanks,

    Jt
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    Fu-Kwun Hwang
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    Reply #17 on: January 13, 2011, 12:13:23 pm » posted from:Taipei,T'ai-pei,Taiwan

    Just double click the downloaded jar file to run it locally.

    You can right click and select "open ejs model" if you want to know how the simulation was created with EJS, and you can modify it and click green triangle to compile new simulation and run it.
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