The applet simulates various vector fields, including spherical, radial, and constant plane. It is a generalized version of an electrostatic field simulation by the same author. The field strength and number of particles simulated are adjustable. Divergence, curl, and potential can be color-coded. Grid lines, potential lines, or streamlines can be displayed. Directions, specific links to the subject and source code are also included.

This simulation illustrates a wide range of 3D vector fields, including spherical, radial, and linear. The fields can be displayed as vectors, particle trajectories, equipotentials, and other options. The number of particles, vectors, or streamlines, and the field strength are adjustable. Directions and source code are also included. This is an extension of a 3D Electric and Magnetic Field viewer from the same author.

The Airborne Infection SEIR Model examines the time evolution of four populations in an epidemic: those who are susceptible to infection, those who have been exposed but do not yet exhibit symptoms, those who are infected and contagious, and those who have recovered from the infection. The SUSCEPTIBLE-EXPOSED-INFECTED-REMOVED (SEIR) Model shows that infection can spread throughout a population in just a matter of days. Infections and viruses can be transmitted relatively easily, or can be prevented all together if certain conditions are satisfied. This model examines the spread of infection in indoor environments and the parameters that shape its transmission. The Airborne Infection SEIR 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 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 map and selecting "Open Ejs Model" from the pop-up menu item.

Algebra One on One is a shareware educational game that teaches users about algebra. Game or practice options are available to test knowledge of the 21 functions covered. Different educational levels, including a help system for beginners, are available.

Arenstorf orbits are closed trajectories of the restricted three-body problem. That is, two bodies of masses µ and 1-µ moving in a circular rotation, and a third body of negligible mass moving in the same plane. The computation of these orbits is very sensible to small errors and are a good test for the accuracy of numerical methods for solving Ordinary Differential Equations. This simulation compares the solution of two of these orbits using both a 4th-order fixed step and a 5(4) variable step Runge-Kutta algorithm. The adaptive solver uses an event to find the period of the orbit and stop there. Both the computations of the adaptive solver and the event are done with the step size and the tolerance indicated. The Arenstorf Orbit JS Model was developed using the Easy Java Simulations (Ejs) version 5. It is distributed as a ready-to-run html page and requires only a browser with JavaScript support.

The EjsS Asset Exchange Model Package contains JavaScript models to investigate the the transfer of wealth in a simple economic model consisting of N buyers and sellers, known as agents, who spend their time buying and selling goods at a yard sale. In this economic model, two agents A and B are chosen at random and goods are exchanged. If the price of the item is correct, neither agent gains or looses wealth but this is uninteresting and unrealistic. In a realistic transaction an agent can either pay too much or get a bargain so that one agent becomes slightly richer while the other agent becomes poorer. What happens to the wealth of agent wA if this process is repeated many times and if we assume that the agent receiving the bargain is chosen at random so that sometimes agent A gains and sometimes agent A looses in the transaction. In other words, neither agent is always shrewd or always gullible so that all agents have an equal chance of getting rich. Does this model produce an equitable distribution of wealth? The EjsS Asset Exchange Model Package was developed using the Easy Java/JavaScript Simulations (EjsS) version 5 authoring tool. Although EjsS is a Java program, it can create stand alone JavaScript programs that run in almost any PC or tablet.

The Bead on a Hyperbolic Tangent model computes the dynamics if a bead constrained to slide on a hyperbolic tangent shaped wire. The model uses an Euler algorithm to evolve the system and it displays the velocity, acceleration, and normal force vectors as the bead slides along the wire. Separate graphs show the energy and force components. The goal of this teaching model is to find the proper acceleration that will guide a particle along an arbitrary single valued function, y=f(x)--in other words, to simulate the classic "bead on a wire." Although there are many methods for doing this, the focus of this work to keep the theory and procedures within the realm of freshman physics. The origins of this work are from an ongoing effort to add computation, in the form of computer animation projects, to the freshman mechanics course. This work is descdribed in the American Journal of Physics (AJP) publication "Computational problems in introductory physics: lessons from a bead on a wire," by T. Bensky and M. Moelter. The Bead on a Hyperbolic Tangent 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 jar file will run the program if Java is installed.

The Binomial Coefficient model displays the number of ways k objects can be chosen from among n objects when order is irrelevant.   This number is known as a binomial coefficient and can be used to predict the the flipping of n coins with equal probability of heads and tails. The Binomial Coefficient 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_stp_BinomialCoefficient.jar file will run the program if Java is installed.

The EJS Binomial Distribution Model calculates the binomial distribution. You can change the number of trials and probability. 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. The Binomial Distribution 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_stp_BinomialDistribution.jar file will run the program if Java is installed. Ejs is a part of the Open Source Physics Project and is designed to make it easier to access, modify, and generate computer models. Additional Ejs models are available. They can be found by searching ComPADRE for Open Source Physics, OSP, or Ejs.

The Brute Force Microstates model considers an isolated system consisting of N identical, non-interacting quantum particles. We wish to determine the total number of system microstates accessible to the system with energy E and hence the entropy.   For distinguishable particles, the simplest brute force method that can be devised involves N nested loops, each over the list of single particle energy levels. This results in a computational scheme that scales exponentially with the system size. Still, this is an instructive method to apply because it shows the rapid increase in the number of microstates for moderate N, and the corresponding exponential increase in computational time. The model displays the computation time as users to vary the number of particles N and the total energy E. The Brute Force Microstates model was developed by Wolfgang Christian, Trisha Salagaram, and Nithaya Chetty using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_stp_BruteForceMicrostates.jar file will run the program if Java is installed.

The Central Force JavaScript Model computes the trajectory of a particle acted on by a central force.  The model reads uses a JavaScript mathematical expression parser to read the force and a adaptive step Runge-Kutta 5(4) algorithm to compute the trajectory.  This model is designed to test the speed of the JS parser and the accuracy of the EJS JavaScript ODE solver. The Central Force JS Model was developed using the Easy Java Simulations (EJS) version 5. It is distributed as a ready-to-run html page and requires only a browser with JavaScript support.

In this experiment, we will discover: 1. how very simple systems can exhibit complex behavior under certain conditions, 2. the richness of the mathematical and physical structure of dynamical systems, 3. how an arbitrarily small change in the input can change the long-term conduct of a dynamical system drastically, 4. how to construct and interpret phase portraits and Poincare Maps for different kinds of responses of a system, 5. the mystery of Fiegenbaum constant and what makes chaos a universal underlying structure of the complexity exhibited by nonlinear dynamical systems, 6. a beautiful and artistic aspect of science in the form of attractors and fractals.

The Circular Well model displays the 2D energy eigenstates of a particle trapped in a very deep two-dimensional circular well.  Because the Schrödinger equation for this system is separable into radial and angular differential equations, the solution can be expressed as a product of a Bessel function and and a complex exponential. The Circular Well model is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_qm_CircularWell.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.

The Complex Function Plot program displays a user-defined complex function of position and time using representations that map phase into color. The default complex function is a time-dependent complex Gaussian and the representation can be changed by selecting a radio button. Additional parameters can be specified using the Display | Switch GUI menu item. Complex Function Plot is an Open Source Physics program written for the teaching of mathematical methods in the sciences. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the math_complex_function_plot.jar file will run the program if Java is installed. Other mathematical methods programs are also available. They can be found by searching ComPADRE for Open Source Physics, OSP, or Math.

This website contains a set of 2 simulations and accompanying worksheets that introduce the techniques of sample mean, hit and miss and importance sampling Monte Carlo integration.

This website contains a simulation and accompanying worksheet that introduces the technique of Smooth Particle Interpolation (SPI), based on Smooth Particle Hydrodynamics (SPH).

The Confined Hard Disk System is an idealized statistical mechanics model that simulates a two-dimensional system of hard disks confined to a box with a constant temperature thermal reservoir at one end and a movable piston at the other. Slow-moving particles are color-coded as blue and fast particles are color-coded as yellow. The model computes and plots the time evolution of the kinetic energy K per particle, the pressure P, and the volume V. The model also displays histograms and mean values of these quantities. The Confined Hard Disk System 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_stp_hd_ConfinedHardDiskSystem.jar file will run the program if Java is installed.

The Confined Hard Disk Two Piston System simulates a constant-energy two-dimensional system of unit mass particles confined by two frictionless pistons of equal mass M. This computer model complements theoretical work describing the adiabatic expansion of an ideal gas using the quasi-static approximation. Users can set the number of particles N, their diameter and their initial particle kinetic energy. Slow-moving particles are color-coded as blue and fast particles are color-coded as yellow. The time evolution of temperature, pressure, and piston speed are shown in a second window.   Particles in this model have unit mass and interact through contact forces. Collision times are computed analytically because particles and pistons move with constant velocity between collisions. The time evolution algorithm advances the particle position from collision to collision until the requested time step is achieved. The time evolution is then paused, data is accumulated, and the screen is redrawn. The Confined Hard Disk Two Piston System 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_stp_hd_ConfinedHardDiskTwoPistonSystem.jar file will run the program if Java is installed.

The Confined Lennard-Jones System is an idealized statistical mechanics model that simulates a two-dimensional system of particles confined to a box with a constant temperature thermal reservoir at one end and a movable piston at the other. Particles in this model have unit mass and interact through pairwise Lennard-Jones forces and hard-wall contact forces. Slow-moving particles are color-coded as blue and fast particles are color-coded as yellow. The model computes and plots the evolution of the total energy E, the kinetic energy per particle K, the pressure P, and the volume V. The model also displays histograms and mean values of these quantities. The Confined Lennard-Jones System 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_stp_md_ConfinedLennardJonesSystem.jar file will run the program if Java is installed.

The Confined Lennard-Jones Two Piston System simulates a constant-energy two-dimensional system of particles confined by two frictionless pistons of equal mass M. This computer model complements theoretical work describing the adiabatic expansion of an ideal gas using the quasi-static approximation. Users can set the initial particle kinetic energy, Lennard Jones parameters, and the initial particle separation. Slow-moving particles are color-coded as blue and fast particles are color-coded as yellow. The time evolution of temperature, pressure, and piston speed are shown in a second window. Particles in this model have unit mass and interact through pairwise Lennard-Jones forces and hard-wall contact forces. The instantaneous temperature is computed using the average particle kinetic energy and the pressure is computed using the virial expansion. The Confined Lennard-Jones Two Piston System is a supplemental simulation for the article "Evolution of ideal gas mixtures confined in an insulated container by two identical pistons" by Joaquim Anacleto, Joaquim Alberto C. Anacleto, and J. M. Ferreira in the American Journal of Physics 79(10), 1009-1014 (2011) and has been approved by the authors and the American Journal of Physics (AJP) editor. The Confined Lennard-Jones Two Piston System 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_stp_md_ConfinedLennardJonesTwoPistonSystem.jar file will run the program if Java is installed.