### Author Topic: Ejs Open Source Real Pendulum Model java applet  (Read 29391 times)

#### lookang

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• http://weelookang.blogspot.com ##### Ejs Open Source Real Pendulum Model java applet
« on: December 12, 2008, 08:54:35 am »
Ejs Open Source Real Pendulum Model java applet modified by lookang
Physical Quantities and Units Measurement of time - Pendulum
Ejs Open Source Pendulum Model java applet
reference:
http://www.compadre.org/osp/items/detail.cfm?ID=7567 by Wolfgang Christian and F. Esquembre

i did not make this!, i am just learning how to make it from the codes.

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!  check out the other pendulums
http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=1823.0 Pendulum by Francisco Esquembre (based on an original algorithm by H. Gould, J. Tobochnik, and W. Christian) Date : February 2002
http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=1606.0 Force analysis of a pendulum by prof Hwang modified by ahmedelshfie
http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=1116.0 Force analysis of a pendulum by prof Hwang
http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=1610.0 Pendulum (Why the angle need to be less than 5 degree --- is it necessary?) by Fu-Kwun Hwang
http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=700.0 Pendulum with damping by Fu-Kwun Hwang
http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=1123.0 large amplitude pendulum by Fu-Kwun Hwang
http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=1807.0 How to combine simulation with a quicktime movie file by Fu-Kwun Hwang
http://youtu.be/t2mhfRzwA0E Julius Sumner Miller - Physics - Pendulums pt. 1
http://youtu.be/LOOhykNHqXM Julius Sumner Miller - Physics - Pendulums pt. 2
http://www.compadre.org/osp/items/detail.cfm?ID=9783 Physical Pendulum Energy written by Mark Matlin

http://physics.bu.edu/~duffy/Ejs/EP_chapter12/pendulum_v2d.html by Andrew Duffy
« Last Edit: August 26, 2011, 03:57:45 pm by lookang »

#### lookang

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• http://weelookang.blogspot.com ##### Re: Physical Quantities and Units Measurement of time - Pendulum lookang
« Reply #1 on: August 03, 2009, 01:59:22 pm »

A simple pendulum is constructed by placing a mass m at the end of a rod of length L with negligible mass. The system oscillates about the lower vertical position due to a torque ? about the pivot produced by gravity acting on the mass. Although a pendulum oscillates, the angle cannot be described by simple trigonometric functions except for small angles. Newton's Law for planar rotation states that the angular acceleration ? of an object is proportional to the torque ? applied to that object
? = I ? .
The constant of proportionality I is known as the moment of inertia and can be shown to be I = mL2 for a mass that is a distance L from the point of rotation. Applying Newton's Second Law for rotation to the pendulum leads to the following second-order differential equation
d2 ? / dt2 = -(g/L) sin( ? ) .
Comparing this dynamical equation to the simple harmonic oscillator differential equation, we see that the pendulum equation undergoes simple harmonic motion for small angles when the approximation ? ~ sin( ? ) is valid. The angular frequency ?= 2?f for this small angle motion is ?= (g/L)1/2.
References:
The Simple Pendulum model is designed to teach Ejs modeling. Right click within the simulation to examine this model in the Ejs modeling and authoring tool. See:
"Modeling Physics with Easy Java Simulations" by Wolfgang Christian and Francisco Esquembre, The Physics Teacher, November 2007, 45 (Cool, pp. 475-480.
The Easy Java Simulations (EJS) manual can be downloaded from the ComPADRE Open Source Physics collection and from the Ejs website.
Note:
This simulation was created by Wolfgang Christian and Francisco Esquembre using the Easy Java Simulations (Ejs) modeling tool. You can examine and modify this simulation if you have Ejs installed by right-clicking within a plot and selecting "Open Ejs Model" from the pop-up menu. Information about Ejs is available at: .

The Pendulum model uses polar coordinates to compute the displacement angle ? but the pendulum bob in the simulation's view is positioned using Cartesian coordinates. We create x and y auxiliary variables to synchronize objects in the view with the model. These Cartesian coordinates are computed from the displacement angle when they are defined and after every animation step using an Ejs Constraints page

Because mouse actions are enabled on the bob's properties page and because the model's x and y variables are bound to the bob's x and y properties, the model's x and y variables change when the bob is dragged. This binding of on-screen properties to a model's internal variables encourages us to define a custom method newPosition that computes the displacement angle ? from the bob's Cartesian coordinates. The newPosition method also sets the bob's velocity components to zero and insures that the final coordinates are the correct distance L from the pivot point. The newPosition method is called in response to a mouse drag by entering the method name as the drag action in the bob's properties page.

« Last Edit: August 26, 2011, 03:47:45 pm by lookang »

#### lookang

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• http://weelookang.blogspot.com ##### Re: Physical Quantities and Units Measurement of time - Pendulum lookang
« Reply #2 on: August 11, 2009, 11:46:28 am »
hotpotato quiz
click on the pendulumperiod.html to launch a quiz question i adapted from a typical pen and paper test.
pendulumperiod.zip is the source of the hot potato http://hotpot.uvic.ca/
« Last Edit: August 25, 2011, 10:02:06 pm by lookang »

#### lookang

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• http://weelookang.blogspot.com ##### Re: Ejs Open Source Real Pendulum Model java applet
« Reply #3 on: August 26, 2011, 03:54:19 pm »
changes:
1 was based on a much earlier version found in Ejs default examples by W. Christian and F. Esquembre
2 added alpha = d(omega)/dt = d2(theta)/dt2 into the model's visualization
3 added color scheme consistent with all my usual simulations
6 made the codes show pendulum consistently for different length L
26 August 2011
added Fdrag = k*omega to simulate air resistance
added time step to allow slow down observation
add theory pendulum Periodtheory = 2*Math.PI*Math.sqrt(L/g); from http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=1610.0 Pendulum (Why the angle need to be less than 5 degree --- is it necessary?) by Fu-Kwun Hwang
add counter to calculate number of complete periods using numberofswing = Math.floor(n1/2);
if(omega*omegas<0){
n1++;

if(n1%2.==0.){
T1[nc]=t-ts;
ts= t;
}
// else T1[nc]=t*2.;// first half period

}
omegas = omega; // to store value of omega
add code to prevent program crashing if (numberofswing>=20.) _pause(); // to prevent error in T1 array
add PE ref to illustrate like tracker can, the meaning of arbitrary reference level

enjoy a new and improved simulation!
« Last Edit: August 26, 2011, 03:57:21 pm by lookang »