Enjoy the fun of physics with simulations!

Backup site http://enjoy.phy.ntnu.edu.tw/ntnujava/

Title: Ejs Open Source Real Pendulum Model java applet Post by: lookang on December 12, 2008, 07:54:35 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. [ejsapplet] 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://phet.colorado.edu/sims/pendulum-lab/pendulum-lab_en.html Pendulum Lab by PhET http://physics.bu.edu/~duffy/Ejs/EP_chapter12/pendulum_v2d.html by Andrew Duffy Title: Re: Physical Quantities and Units Measurement of time - Pendulum lookangPost by: lookang on August 03, 2009, 12:59:22 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 τ 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 α of an object is proportional to the torque τ applied to that object τ = I α . 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 θ / dt2 = -(g/L) sin( θ ) . 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 θ ~ sin( θ ) is valid. The angular frequency ω= 2πf for this small angle motion is ω= (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 θ 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 θ 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. CLick on ejs_Pendulumwee.jar to downloadTitle: Re: Physical Quantities and Units Measurement of time - Pendulum lookangPost by: lookang on August 11, 2009, 10:46:28 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/ Title: Re: Ejs Open Source Real Pendulum Model java applet Post by: lookang on August 26, 2011, 02:54:19 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 4 added velocity visualization 5 added context of ceiling 6 made the codes show pendulum consistently for different length L 26 August 2011 added special menu drop from g following Phet design http://phet.colorado.edu/sims/pendulum-lab/pendulum-lab_en.html Pendulum Lab by PhET added Fdrag = k*omega to simulate air resistance added time step to allow slow down observation add forces mg and tension add energy bars 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[100] array add PE ref to illustrate like tracker can, the meaning of arbitrary reference level enjoy a new and improved simulation! |