### Author Topic: Ejs Open Source Horizontal Circular Motion of Mass on a table java applet  (Read 14847 times)

#### lookang

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##### Ejs Open Source Horizontal Circular Motion of Mass on a table java applet
« on: July 04, 2010, 09:24:26 pm »
Ejs Open Source Horizontal Circular Motion of Mass on a table java applet
http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=1454.0

this applet is customized to allow visualization & sense making of circular motion of the case of Horizontal Circular Motion of Mass on a table.
Conservation of Angular momentum and 3D circular motion
A particle with mass m is moving with constant speed v along a circular orbit (radius r).
gravitational force Mg from another mass M hanging from the string, provides the centripetal acceleration for horizontal circular motion of mass m.
A string is connected from mass m to the origin ( a hole for the string to pass in through) then connected to mass M.
This model assume conservation of angular momentum \$vec{L}=m,vec{r}   imes vec{v}\$ . i.e. \$L=mr^2omega\$ is a constant.
For particle with mass m:
\$m frac{d^2r}{dt^2}= m frac{v^2}{r}-Mg=frac{L^2}{mr^3}- Mg\$
\$omega=frac{L}{mr^2}\$
You should change radius only for perfect circular motion, changing M or m will result additional radial acceleration which then the motion is not circular but elliptical.
I would like to thank Prof Hwang Fu-Kwun for his superb guidance and masterful support that facilitated my self directed informal learning and collaborate with world-class physicists to make customize applets for the general well being of the world.
And Prof Paco for creating easy java simulation! and 3D java rocks! but there are some bugs (can toggle to Java3D to test, it will hang) await for improved releases of Ejs4.3.0!

Full screen applet or Problem viewing java?Add http://www.phy.ntnu.edu.tw/ to exception site list
• 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!
« Last Edit: July 08, 2010, 09:28:57 am by lookang »

#### lookang

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##### Re: Ejs Open Source Horizontal Circular Motion of Mass on a table java applet
« Reply #1 on: July 04, 2010, 09:25:22 pm »

1 added text into the source codes
2 verified the physics of CO angular Momentum in the codes
3 added contact force N, weight mg and tension T
5 added angular displacement theta, angular velocity omega, time t, centripetal acceleration a
7 change some color scheme
8 add some slider and bars to show values
9 design all variables to be drawn in 3D with checkboxes for sense making
10 decode the Conservation of Angular momentum and 3D circular motion with my T1 = m*v*v/r + m*dvr/dt ? // radial acceleration due to tangential change in velocity and radial acceleration due to radial change in velocity ? where dvr/dt = (cst*cst/(m*r*r*r)-M*g)/m
11 too tired to write compare http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=1454.0 with this post to know changes made by me
12 changed back to simple 3D default because Java 3D still improving.
13 change the table to current color scheme for faster rendering
« Last Edit: July 08, 2010, 12:27:29 am by lookang »

#### Fu-Kwun Hwang

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##### Re: Ejs Open Source Horizontal Circular Motion of Mass on a table java applet
« Reply #2 on: July 07, 2010, 10:51:00 pm »
Java 3D look nice. However, most of the users might not be able to see it.
I can not see it on web version,too!

May be you can have two versions, one without java3D ,and add another downloadable jar file for java3D.

#### lookang

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##### Re: Ejs Open Source Horizontal Circular Motion of Mass on a table java applet
« Reply #3 on: July 07, 2010, 11:44:39 pm »
java.lang.NullPointerException
at users.sgeducation.lookang.circular3dfr02_pkg.circular3dfr02View.reset(circular3dfr02View.java:1560)
at org.colos.ejs.library.Animation.reset(Unknown Source)
at users.sgeducation.lookang.circular3dfr02_pkg.circular3dfr02Simulation.(circular3dfr02Simulation.java:25)
at users.sgeducation.lookang.circular3dfr02_pkg.circular3dfr02.(circular3dfr02.java:93)
at users.sgeducation.lookang.circular3dfr02_pkg.circular3dfr02Applet.init(circular3dfr02Applet.java:27)
at sun.applet.AppletPanel.run(AppletPanel.java:424)
at jep.AppletFramePanel.run(Unknown Source)

same on the Mac.

will make default simple 3D

YouTube. Was stuck at Portland airport from 11pm to 4am, decided to use the time to make some promotional video on the applets shared during 2010 AAPT Summer Meeting in Portland, Oregon
« Last Edit: July 26, 2010, 10:32:41 pm by lookang »

#### ahmedelshfie

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##### Re: Ejs Open Source Horizontal Circular Motion of Mass on a table java applet
« Reply #4 on: July 08, 2010, 12:24:21 am »
Nice java 3d look beautiful,, i test by HTML and work very well.
Any way i like version java 3D good job

#### lookang

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##### Re: Ejs Open Source Horizontal Circular Motion of Mass on a table java applet
« Reply #5 on: July 08, 2010, 09:30:48 am »
Nice java 3d look beautiful,, i test by HTML and work very well.
Any way i like version java 3D good job
i like java 3D too, but just be aware, it may fail for complex simulations.
the above applet get stuck sometimes in java3D mode.

#### lookang

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##### Re: Ejs Open Source Horizontal Circular Motion of Mass on a table java applet
« Reply #6 on: July 12, 2010, 01:42:04 pm »
09 July 2010 Computer Lab hands on learning session on Ejs Open Source Vertical Circular Motion of mass m attached to a rod java applet 3D view with teacher demo and student working on their own desktop

09 July 2010 Computer Lab hands on learning session on  Ejs Open Source Vertical Circular Motion of mass m attached to a rod java applet 3D view with teacher explaining and student working on their own desktop

09 July 2010 Computer Lab hands on learning session on  Ejs Open Source Vertical Circular Motion of mass m attached to a rod java applet side view of the same 3D view with teacher explaining the physical setup of the mass m and mass M attached by a string through a table with a fricitionless hole in the middle of table for string to go through and student working on their own desktop
http://sgeducation.blogspot.com/2010/07/lesson-on-circular-motion-with-acjc.html
« Last Edit: July 12, 2010, 01:44:12 pm by lookang »