Molecular Model Project

The Ejs N-body Orbits model displays the dynamics of three to five identical masses orbiting each other subject to Newtonian gravity. The simulation displays the periodic orbital motion of the masses. The initial configuration of the system can be changed via slider. You can modify this...

The Ejs Doppler Effect model displays the detection of sound waves from a moving source and the change in frequency of the detected wave via the Doppler effect. In addition to the wave fronts from the source a graph depicting the time of emission and time of detection of each of the wave fronts...

The Ejs Circumnavigating Pendulum model displays the dynamics of a mechanical oscillator in uniform circular motion. The mechanical oscillator is free to move in two directions. This 2-dimensional simulation displays all the dynamical features of the Foucault pendulum, except for the dependency...


Platforms: Mac

The Lennard-Jones Fluid 2D program shows a system of particles in two dimensions interacting via the Lennard-Jones potential. The program displays the particles in the box as a function of time once the partition dividing the box into three parts are removed. The program is distributed as a...


Platforms: Mac

The Ejs Orbiting Mass on a Table 3D model displays the frictionless dynamics of two masses that are attached via a string through a hole in a horizontal table. Mass m moves on the table in two dimensions while mass M hangs vertically and just moves up and down. The simulation allows displaying...


Platforms: Mac

The EJS Radioactive Decay Model simulates the decay of a radioactive sample using discrete random events. It displays the number of radioactive nuclei as a function of time. You can change the initial number of nuclei and the decay constant as well as changing the plot to a semi-log plot. The...


Platforms: Mac

The Ejs Driven Diatomic Oscillator Chain model displays a one-dimensional diatomic chain of coupled harmonic oscillators with one end driven by an external force and the other end attached to a sliding rod shock absorber. The mass and Stoke's Law damping for the shock absorber are chosen to...


Platforms: Mac

The EJS Magnetic Bar Field Model shows the field of a bar magnet and has a movable compass that reports the magnetic field values. The bar magnet model is built by placing a group of magnetic dipoles along the bar magnet. You can modify this simulation if you have Ejs installed by right-clicking...


Platforms: Mac

The Ejs Duffing Oscillator model computes the solutions to the non-linear Duffing equation, which reads, x'' + 2?zN*x' - x (1 - x2) = f cos(?Ya*t), where each prime denotes a time derivative. The simulation displays the solution as well as the phase space and Poincare plots, and energy diagram....


Platforms: Mac

The Ejs Phase Space Plotter model displays the dynamics of an ensemble of pendula or simple harmonic oscillators in phase space (velocity versus position). Friction is initially set to zero but can be changed via a textbox as can the number of elements in the ensemble. For the pendulum ensemble,...


Platforms: Mac

The Partitioned Box program displays the number of particles on one half of a box as a function of time after a small hole is made in the partition dividing the box in half. The purpose of this simulation is to gain insight into the tendency of macroscopic systems to approach a well defined...


Platforms: Mac

The Ejs Lagrange Top model displays the motion of a heavy symmetric top under the effect of gravity. The top has an initial angular speed that provides the precessional, nutational, and rotational speeds. The ratio of Lz to Lx can be set via slider and the initial angular position and angular...


Platforms: Mac

The Ejs Inertial Oscillation model displays the motion of a particle moving over the surface of an oblate spheroid. The spheroid is flattened to an ellipsoid of revolution because it is rotating, just as the Earth is flattened because it is rotating. The particle is confined to motion along the...


Platforms: Mac

The EJS Equinox Precession model illustrates the Copernican theory of Earth's orbit around the sun. The top window shows a view from outside the celestial sphere. The simulation shows the moving Earth along with its axis or rotation and the line of sight from Earth, through Sun, to the Celestial...


Platforms: Mac

The Ejs Coin Rolling without Sliding on an Accelerated Platform model displays the dynamics of a coin rolling without slipping on an accelerated platform. The simulation displays the motion of the coin as well as the velocity vectors for the surface of the coin and the platform. The initial...


Platforms: Mac

The Ejs Damped Driven Harmonic Oscillator Phasor model displays the motion of damped driven harmonic oscillator. The resulting differential equation can be extended into the complex plane, and the resulting complex solution is displayed with the real part of this solution being the position of...


Platforms: Mac

The Ejs Quartic Oscillator model displays the motion of a bead moving without friction along a horizontal rod, while tied to two symmetric springs. Both the motion of the masses and the phase space plot are shown in the simulation. The natural length of the springs can be changed via textboxes....


Platforms: Mac

The Ejs Normal Modes on a Loaded String model displays the motion of a light string under tension between two fixed points. The string is also loaded with N masses located at regular intervals. The number of masses on the string can be changed via textboxes. You can modify this simulation if you...


Platforms: Mac

The Ejs Strange Harmonic Oscillator model displays the motion of two masses connected by a massless rigid rod and the masses may move without friction along two perpendicular rails in a horizontal table. The energy of the oscillator system can be changed via a slider. You can modify this...


Platforms: Mac

The Ejs Keplerian Orbit model displays the dynamics of a mass orbiting a much larger mass subject to Newtonian gravity. The simulation displays the motion of the smaller mass and the effective potential energy diagram. The initial energy of the system can be changed via textbox and the initial...


Platforms: Mac