New Open Source Physics collection resources

Modeling a Hot Wheels Loop

Tue, 31 Jan 2012 13:33:36 EST

In this activity a Tracker model is compared with a toy truck attempting to drive up and around a Hot Wheels vertical loop track. Three different videos show the truck entering the loop at different speeds. For related EJS models see Particle Motion On A Curve and Particle Motion On A Vertical Elliptical Loop. The zip file includes all three videos and pdf instructions.

Sliding down the Subway: Inclined Plane

Tue, 31 Jan 2012 13:13:31 EST

The Sliding down the Subway exercise is a video analysis of a person sliding down a slide installed over a set of stairs in a subway (as part of the VW Fast Lane Series). The zip file contains the video, instructions and the Tracker file. Credits: The original video came from Volkswagen: http://www.youtube.com/watch?v=W4o0ZVeixYU. To open the Tracker file, download and run Tracker from http://www.cabrillo.edu/~dbrown/tracker/. Tracker is free.

Logistic Map Fixed Points Model

Sun, 29 Jan 2012 16:37:51 EST

The Logistic Map Fixed Points Model finds periodic trajectories of the logistic map such that n iterations of the map starting with an initial value x return to that value. The key idea for this model is that for values of the logistic map control parameter r in the chaotic regime, there are periodic but unstable trajectories. This property of the chaotic regime means that if we choose the value of the seed x0 to be precisely equal to a point on an unstable trajectory with period n, the subsequent trajectory will have this period. However, if we choose a value of x0 that differs ever so slightly from this special value, the trajectory will not be periodic. This model shows how to find these special values of x0. The Logistic Map Fixed Points Model was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_chaos_LogisticMapFixedPoints.jar file will run the program if Java is installed.

Rally Car Jump Model

Sun, 22 Jan 2012 20:41:48 EST

The Rally Car Jump Model simulates the effect of a rally car jumping off of a ramp as in an X Games event. The simulation make the approximation that the car's rear wheels move along the ramp at a constant speed until the end of the ramp is reached. The rally car experiences a torque, and hence a rotation, when the front wheels lose contact with the ramp. Once the rear wheels also leave the ramp, the rotation rate stays fixed until the car hits the second ramp. The Rally Car Jump Model was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the jar file will run the program if Java is installed.

Ferris Wheel Model

Sun, 22 Jan 2012 20:25:36 EST

The Ferris Wheel Model explores the amusement park ride modeled after Ferris' original wheel. The simulation shows a wheel that can be varied in radius from 40 m (Ferris' original wheels) to 100 m, or about 10 meters langer than the current world record. In addition, the rotational speed of the wheel can be varied from -20 m/s to 20 m/s. By selecting the checkbox, the free-body diagram can be shown. The Ferris Wheel Model was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the jar file will run the program if Java is installed.

OSP Tools and the ComPADRE OSP Collection

Sat, 21 Jan 2012 09:00:56 EST

This paper outlines the pedagogical and technical features of the Open Source Physics (OSP) project and how we use OSP-based tools and resources to introduce modeling into the curriculum. We describe our current effort to create and distribute new material using the Easy Java Simulations and Tracker tools and how we distribute this curricular material with ComPADRE National Science Digital Library [OSP 2009]. The paper is organized as follows. Section II introduces the Modeling Cycle that is the basis for our pedagogy. Section III describes basic Easy Java Simulations concepts and section IV describes Tracker. The main features of ComPADRE are presented in section V and section VI presents the pedagogical benefits of this connection. Finally, section VII summarizes the improvements obtained by the use of our approach.

Parallel Region Prime Number Computation Model

Thu, 19 Jan 2012 07:52:05 EST

The Parallel Region Prime Number Computation Model uses the prime division algorithm to decide if a number is prime. The prime division algorithm is inefficient and we use it here only to test the EJS implementation of the Parallel Region Element in EJS. A parallel region executes independent code in a separate thread and these threads can execute simultaneously on a multi-core processor. The screen capture shows that the total execution time for four computations on a quad-core processor is only one millisecond longer than the execution time for the longest single computation. This linear speedup is close to the theoretical maximum. The Parallel Region Prime Number Computation Model was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the model's jar file will run the simulation if Java is installed.

Fluorescence Spectra

Tue, 17 Jan 2012 19:57:02 EST

This experiment uses the Tracker video analysis and modeling tool to explore the phenomenon of fluorescence and its application in fluorescent lamps. For each of five different visible spectra, students (a) observe the spectrum directly, (b) measure its brightness versus wavelength in Tracker, and (c) answer both qualitative and quantitative questions about it. The spectra include a fluorescent dye with laser and UV illumination, a mercury lamp and two fluorescent lamps, all with red and green laser spots added for easy calibration. For more information, see the AAPT presentation item 9685. The zip file includes the lab instructions, spectrum images and Tracker data files. This requires Tracker version 4.62 or higher. Tracker installers are available for Windows, Mac and Linux from ComPADRE or the Tracker web site (http://www.cabrillo.edu/~dbrown/tracker/).

Merry Mixer Ride Model

Sun, 15 Jan 2012 19:00:30 EST

The Merry Mixer Ride Model shows the motion of two superimposed circular motions. The main frame of the ride rotates in one direction, while a second rotation at the ends of the frame arms carries the riders in an additional circular motion, ususally in the opposite direction. In this simulation, the operator controls the two rotation rates as well as the radii of the two orbits. The systems response to changes in controls is lagged to prevent unphysical accelerations of riders. Remember to let the simulation run for several seconds after adjusting controls for the changes to settle in. The Merry Mixer Ride Model was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the jar file will run the program if Java is installed.

Simple Circular Motion Model

Sun, 15 Jan 2012 18:31:23 EST

The Simple Circular Motion Model explores amusement park rides like a Merry-Go-Round. The rotational speed and radial distance are controlled with sliders at the bottom of the applet. The controls are "lagged" to reduce the unphysical results of "slamming" the simulation controls. The net horizontal force on the riders is monitored in the accompanying graph in terms of "g's", that is, in terms of multiples of the rider's weight. The Simple Circular Motion Model was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the jar file will run the program if Java is installed.

Free Fall Ride Model

Sun, 15 Jan 2012 12:49:57 EST

The Free Fall Ride Model allows a user to design a ride by adjusting the height versus time graph. The apparant weight of the rider arises from the ever present acceleration of gravity in combination with the acceleration of the elevator. If the elevator is stationary or moving with consant speed (i.e. not accelerating), the rider feels their normal weight. If the elevator accelerates upwards, the rider feels heavier and if the elevator accelerates downward the rider feels lighter. With a strong enough downward acceleration, the rider can experience effective weightlessness or even negative g forces (requiring seat belts or restraints to avoid head trauma!). The Free Fall Ride Model was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the jar file will run the program if Java is installed.

Swing Ride Model

Sun, 15 Jan 2012 11:46:09 EST

The Swing Ride Model simulates a type of ride that can be found at many carnivals and amusement parks. Riders are suspended from the ends of supports. These supports rotate about an axis that can be tilted with respect to the vertical. In this simulation the controls are lagged to prevent unrealistic changes to the physical system. The Swing Ride Model was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the jar file will run the program if Java is installed.

Pirate Ship Ride Model

Sun, 15 Jan 2012 10:49:36 EST

The Pirate Ship Ride Model was originally inspired by the Pirate Ride at Hershey Park. The "ship" part of the ride has a center of mass that lies 14 m from the pivot point (approximately the center of the boat). The ship swings freely from the pivot, and is driven by a roller built into the floor directly below the ship. The operator presses either the clockwise torque button or the counter clockwise torque button to change the motion of the ship. Because the drive can only push the ship when it is in contact, the drive is only available when the ship is within 30º of its lowest postion. The drive buttons are grey when no drive is available (simulation is paused or the ship coes not contact the drive roller), the turn white when the drive is available. When drive button is pressed, it turns green and a constant torque is exerted on the ship unitl the button is released or until the ship moves out of contact with the drive roller. Note that torque can not be applied if the simulation is paused or has not been started. The Pirate Ship Ride Model was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the jar file will run the program if Java is installed.

Bungee Jumping Model

Sun, 15 Jan 2012 10:24:40 EST

In the Bungee Jumping Model, a bungee jumper is dropped from a tower with a fixed length of bungee cord. The simulation operator can control the height of the tower, the stiffness of the bungee cord (determined by its spring constant k), the unstretched length of the bungee cord and the jumper's mass. The player buttons are the play/pause button, the rewind (to t=0) button and the reset button (resets all parameters to initial values). The operator may optionally display the forces acting on the jumper and a plot of the g-forces versus time. Note that the simulation measures the altitude in terms of the location of his feet, thus he hits the ground if his feet get within his 1.7m of height to the ground. The Bungee Jumping Model was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the jar file will run the program if Java is installed.

Talk: Using Tracker to Measure the Length of the Sidereal Day

Sat, 14 Jan 2012 20:55:03 EST

This talk describes how we use the Tracker video analysis and modeling program to analyze still images. We have used a group of still 30-second images taken 9 ½ minutes apart (for 10 minutes between images). To analyze these images we use Tracker. We use the feature in Tracker which automatically creates a “movie” of still images and then allows the user to define the time interval between images. In this talk we show our preliminary results and propose possible future improvements. The Open Source Physics Project is generously supported by the National Science Foundation (DUE-0442581).

Xuggle Installers

Wed, 11 Jan 2012 08:52:02 EST

The OSP Project has adopted the open-source Xuggle video engine to read and write video clips using Java. The Xuggle engine is composed of two main components; a set of Java jar files, and a set of native shared libraries (.dll files on Windows, .so files on Linux, or .dylib files on Mac). Although the Xuggle engine is installed automatically when the Tracker video analysis and modeling tool is installed, other OSP programs, such as Easy Java Simulations, do not automatically install Xuggle. The Xuggle installers available here install the necessary files. Note: Tracker users do not need to use the Xuggle installers because Tracker automatically installs the Xuggle video engine. The OSP Xuggle installers are available on Linux, Mac OS X, and Windows.

Xuggle Windows Installer
Xuggle Mac OS X Installer - Mac users running OSP programs with a 64-bit OS (Snow Leopard or Lion) may wish to see this discussion.
Xuggle Linux 32-bit Installer
Xuggle Linux 64-bit Installer

Measurement of the Solar Rotation Rate with Tracker

Mon, 09 Jan 2012 15:14:34 EST

The Measurement of the Solar Rotation Rate with Tracker Lab uses the Tracker video analysis tool to measure and analyze the motion of sunspots to determine the solar rotation rate. This exercise uses 31 still images taken 1 day apart of the Sun. Images taken by the SOHO satellite. Requires Tracker version 4.6 or greater. The zip file contains the lab instructions, the series of still images that will be made into a movie, and a sample Tracker file. Measurement of the Solar Rotation Rate with Tracker Lab is one of several Tracker models used to incorporate computational and video analysis techniques in introductory astronomy. Tracker, a video analysis program with dynamical modeling, is an Open Source Physics tool.

Measurement of the Sidereal Day with Tracker

Mon, 09 Jan 2012 14:44:07 EST

The Measurement of the Sidereal Day with Tracker Lab uses the Tracker video analysis tool to measure and analyze the motion stars near Polaris (the North Celestial Pole) to determine the length of the sidereal day. This exercise uses 13 still images taken 10 minutes apart of the night sky near Polaris. Requires Tracker version 4.6 or greater. The zip file contains the lab instructions, the series of still images that will be made into a movie, and a sample Tracker file. Measurement of the Sidereal Day with Tracker Lab is one of several Tracker models used to incorporate computational and video analysis techniques in introductory astronomy. Tracker, a video analysis program with dynamical modeling, is an Open Source Physics tool.

Spline Potential Eigenfunctions Model

Mon, 09 Jan 2012 07:44:35 EST

The Spline Potential Eigenfunctions Model computes the Schrödinger equation energy eigenvalues and eigenfunctions for a particle confined to a potential well with hard walls at -a/2 and a/2 and a smooth potential energy function between these walls. The potential energy function is a third-order piecewise continuous polynomial (cubic spline) that connects N draggable control points. Cubic-spline coefficients are chosen such that the resulting potential energy function and its first derivative is smooth throughout the interior and has zero curvature at the endpoints. Users can vary the number of control points and can drag the control points to study level splitting in multi-well systems. Additional windows show a table of energy eigenvalues and their corresponding energy eigenfunctions. The Spline Potential Eigenfunctions Model was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_qm_SplinePotentialEigenfunctions.jar file will run the program if Java is installed.

Diffusion Limited Aggregation in Continuous 2D Space Model

Sat, 07 Jan 2012 18:56:30 EST

The Diffusion Limited Aggregation in Continuous 2D Space Model simulates the formation of a cluster using a random-walk process called "diffusion limited aggregation" (DLA). The cluster formed by this process is an example of a fractal, and the simulation can be extended to calculate and analyze the fractal dimension. The Diffusion Limited Aggregation in Continuous 2D Space Model was developed using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_fmu_DLA_continuous_2D.jar file will run the program if Java is installed. You can modify this simulation if you have EJS installed by right-clicking within the plot and selecting "Open Ejs Model" from the pop-up menu item.