The EJS Anisotropic Oscillator model displays the dynamics of a mass connected to two opposing springs. The simulation displays the motion of the mass as well as the trajectory plot. The initial position of the mass can be changed by dragging. The unstretched lengths of the springs can changed as well via textboxes.

The EJS Beats model displays the result of adding two waves with different frequencies. The simulation displays the superposition of the two waves as well as a phasor diagram that shows how the waves add up at one point in space. The ratio of the wave amplitudes, the ratio of the frequencies, and the phase shift between the two waves can be changed via textboxes.

This activity enables students to calculate the speed of sound in a laboratory setting.

The EJS Coupled Oscillators and Normal Modes model displays the motion of coupled oscillators, two masses connected by three springs. The initial position of the two masses, the spring constant of the three springs, the damping coefficient for each mass, and the driving force and driving force frequency for the left mass can be changed via text boxes.

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 the oscillator. The natural frequency of the oscillator, the damping coefficient, and the driving force and driving frequency can be changed via textboxes.

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.

The EJS Oscillations and Lissajous Figures model displays the motion of a superposition of two perpendicular harmonic oscillators. The simulation shows the result of the superposition. The amplitude and frequency of the oscillators can be changed via textboxes.

The EJS Wave Representations model displays two representations of a sinusoidal wave on a string. One shows a movie of the wave traveling along a string - you can think of this representation as a sequence of photographs. The second representation is a plot of the displacement as a function of time for two points on the string (you can select which two points to use). Using only these two representations, you can determine the values of many different parameters that describe the wave.

The EJS Harmonics and Fourier Series model displays the sum of harmonics via a Fourier series to yield a new wave. The amplitude of each harmonic as well as the phase of that harmonic can be changed via sliders. In addition, several pre-set functions can be chosen to display. 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 EJS Oscillator Chain model shows a one-dimensional linear array of coupled harmonic oscillators with fixed ends. This model can be used to study the propagation of waves in a continuous medium and the vibrational modes of a crystalline lattice. The EJS model shown here contains 31 coupled oscillators equally spaced within the interval [0, 2 pi] with fixed ends.

The EJS Pendulum on an Accelerating Train model displays the model of a pendulum on an accelerating train. The problem assumes that the pendulum rod is rigid and massless and of length, L = 2, and the pendulum bob is of mass, m = 1. The initial pendulum angle and the initial velocity of the train can be changed via textboxes, and the acceleration of the train can be changed via a slider.

The EJS Platform on Two Rotating Cylinders model displays the model of a platform resting on two equal cylinders are rotating with opposite angular velocities. There is kinetic friction between each cylinder and the platform. The separation between the cylinders and the coefficient of kinetic friction can be changed via textboxes.

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.

This inquiry lab activity involves students working to understand that sound is made from vibrations.

The EJS Spinning Hoop model displays the model of a bead moving along a hoop which is spinning about its vertical diameter with constant angular velocity ?. Friction is negligible. The simulation displays the motion of the bead as well as a plot of angle vs. time for the bead. The angular velocity of the hoop and the starting angle of the bead can be changed via sliders.

The EJS Spring Pendulum model displays the model of a hollow mass that moves along a rigid rod that is also connected to a spring. The mass, therefore, undergoes a combination of spring and pendulum oscillations. The initial position and velocities, as well as the spring constant can be changed via textboxes.