# NTNUJAVA Virtual Physics LaboratoryEnjoy the fun of physics with simulations! Backup site http://enjoy.phy.ntnu.edu.tw/ntnujava/

## JDK1.0.2 simulations (1996-2001) => Dynamics => Topic started by: Fu-Kwun Hwang on January 29, 2004, 05:31:05 pm

Title: Blocks and center of gravity
Post by: Fu-Kwun Hwang on January 29, 2004, 05:31:05 pm
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?

-*-

Title: topic10
Post by: Fu-Kwun Hwang on March 30, 2005, 03:51:47 pm
New version

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Title: Re: Blocks and center of gravity
Post by: j142 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

Title: Re: Blocks and center of gravity
Post by: Fu-Kwun Hwang 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.

Title: Re: Blocks and center of gravity
Post by: j142 on January 23, 2009, 01:56:57 pm
Ok

Thank you

Very nice simulation.

Title: Re: Blocks and center of gravity
Post by: jiaen on April 09, 2009, 02:30:03 am
Thank you for this nice applet.  :)

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!

Title: Re: Blocks and center of gravity
Post by: yimseo on May 08, 2010, 09:18:58 pm
Sorry, But i can't view the simulation how?

Title: Re: Blocks and center of gravity
Post by: jenny.smith on July 23, 2010, 08:00:48 pm
@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.

Title: Re: Blocks and center of gravity
Post by: anntaylor on September 16, 2010, 06:41:34 pm
I think it has some error it can't simulate for me.

Title: Re: Blocks and center of gravity
Post by: lookang 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

Title: Re: Blocks and center of gravity
Post by: ahmedelshfie on September 16, 2010, 07:09:46 pm
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.

Title: Re: Blocks and center of gravity
Post by: kddesigns247@yahoo.com on September 18, 2010, 07:21:33 am
Tried to copy paste did not work, please let me know have a MAC computer anyone know?

Title: Re: Blocks and center of gravity
Post by: Fu-Kwun Hwang on September 18, 2010, 08:11:08 am

Title: Re: Blocks and center of gravity
Post by: anntaylor on December 21, 2010, 05:55:29 pm
zip folder is not opening and showing corrupt file error

Title: Re: Blocks and center of gravity
Post by: Fu-Kwun Hwang on December 21, 2010, 06:09:54 pm
You might want to try to download it again. (Close the browser first and re-open it).
Otherwise, you will only get cached file.

Title: Re: Blocks and center of gravity
Post by: anntaylor on December 22, 2010, 04:28:30 pm
Thanks, Yes now its working I think first download file is not completed.

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Title: Re: Blocks and center of gravity
Post by: jt11347 on January 13, 2011, 10:57:02 am
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

Title: Re: Blocks and center of gravity
Post by: Fu-Kwun Hwang on January 13, 2011, 12:13:23 pm