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Tuesday, August 28, 2012

Ejs Open Source Wave Machine Model Java Applet

Ejs Open Source Wave Machine Model Java Applet by Wolfgang Christian,  this remixed version by lookang.

Ejs Open Source Wave Machine Model Java Applet
http://weelookang.blogspot.sg/2012/08/ejs-open-source-wave-machine-model-java.html
author: Wolfgang Christian, this remixed version is by lookang,
https://dl.dropboxusercontent.com/u/44365627/lookangEJSS/export/ejs_model_WaveMachinewee.jar
https://dl.dropbox.com/u/44365627/lookangEJSworkspace/export/ejs_WaveMachinewee.jar
customized to video here for inquiry http://www.nationalstemcentre.org.uk/elibrary/resource/2096/wave-machine 


Full screen applet
Java Simulation above is kindly hosted by NTNUJAVA Virtual Physics Laboratory by Professor Fu-Kwun Hwang
http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=2545.0
alternatively, go direct to http://www.phy.ntnu.edu.tw/ntnujava/index.php?board=28.0
Collaborative Community of EJS (Moderator: lookang) and register , login and download all of them for free :) This work is licensed under a Creative Commons Attribution 3.0 Singapore License
Author: Wolfgang Christian and lookang (this remix version)
original OSP model by Wolfgang Christian is from here http://www.compadre.org/osp/items/detail.cfm?ID=10481&S=7


Wave Machine by Wolfgang Christian, some minor edits by lookang
The Wave Machine model simulates the wave machine produced by John Shive at Bell Laboratories and made famous by the PSSC Simple Waves film. The machine consists of n horizontal rods with moment of inertia In welded to an axle torsion bar that is perpendicular to the rods. The simulation allows the user to change the lengths of the rods, thereby simulating the effect of a wave propagating in a non-uniform medium. The default rods of length L=2 has a moment of inertia of one
using http://hyperphysics.phy-astr.gsu.edu/hbase/mi2.html I = 1/12 M*L^2 = 1/12 M*2^2 imply 3 = M.
The maximum allowed rods length is 4 giving a moment of inertia of 4 because I = 1/12 3*4^2 = 4
and the minimum allowed length is 1/2 giving a moment of inertia of 1/16. because I = 1/12 3*(0.5)^2 = 1/16.

Twisting rods about the torsion bar causes the rods to oscillate because the bar produces a restoring torque. Because a rods twist acts on neighboring rods, the motions are coupled and a traveling wave results. The speed of the wave depends on the torsional coupling between rods due to torsional bar, k and the moments of inertia of the rods. A damping force can also be added using the model's damping parameter b for the axle torsional bar.

The simulation allows various pulse shapes to be sent down the machine by twisting the first rod with the desired functional form or by dragging the first rod. For example, applying a Gaussian twist produces a Gaussian traveling pulse but the width of this pulse depends on the wave speed. The far end of the wave machine can be free or clamped and this changes the nature of the reflected wave.

Theoretical note: The pulse shape will distort as the wave propagates on the wave machine because of dispersion effects. This distortion is most apparent as the wavelength (or pulse width) approaches the rod separation. Use the Driven Wave Machine model to explore dispersion these effects.

The Wave Machine model is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_mech_osc_chains_WaveMachine.jar file will run the program if Java is installed. Other coupled oscillator models are available. They can be found by searching the OSP Collection for coupled oscillations.

References:
  1. "Standing waves in a non-uniform medium," Paul Gluck, The Physics Teacher, (in press).
  2. "Making waves: A classroom torsional wave machine (Part I)," Kenneth D. Skeldon, Janet E. Milne, Alastair I. Grant, and David A. Palmer Phys. Teach. 36, 392 (1998)
  3. "Making waves: A classroom torsional wave machine (Part II)," Kenneth D. Skeldon, Janet E. Milne, Alastair I. Grant, and David A. Palmer Phys. Teach. 36, 466 (1998)
  4. University of Maryland Physics Lecture-Demonstration website section G3 http://www.physics.umd.edu/lecdem/services/demos/demosg3/demosg3.htm
  5. Similarities in wave behavior, John N. Shive, Bell Telephone Laboratories (1961). See also Am. J. of Physics 32, p572 (1964).
Credits:
The Wave Machine model was created by Wolfgang Christian using the Easy Java Simulations (EJS) version 4.3 authoring and modeling tool created by Francisco Esquembre.

You can examine and modify this compiled EJS model if you run the model (double click on the model's jar file), right-click within a plot, and select "Open EJS Model" from the pop-up menu. You must, of course, have EJS installed on your computer. Information about EJS is available at: and in the OSP ComPADRE collection .

animation of a wave machine with masses of single cycle sine curve generated reaching the other end which is not fixed
animation of a wave machine with no extra masses of single cycle sine curve generated reaching the other end which is not fixed


animation of a wave machine with masses of single cycle sine curve generated reaching the other end which is not fixed

animation of a wave machine with masses of 4 cycles of sine curve generated reaching the other end which is not fixed, to result in a stationary wave

contributed to wikimedia
http://en.wikipedia.org/wiki/John_N._Shive#Shive_wave_machine
http://commons.wikimedia.org/wiki/File:Wavemachine.gif

The Wave Machine model simulates the wave machine produced by John Shive at Bell Laboratories and made famous by the PSSC Simple Waves film. The machine consists of 64 horizontal rods welded to an axle torsion bar that is perpendicular to the rods.
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