Understanding Resonance Graphs Using Easy Java Simulations (EJS) and Why We Use EJS

This paper reports a computer model simulation created using Easy Java Simulation (EJS) for learners to visualize how the steady-state amplitude of a driven oscillating system varies with the frequency of the periodic driving force. The simulation shows (N = 100) identical spring-mass systems being subjected to (1) a periodic driving force of equal amplitude but different driving frequencies, and (2) different amounts of damping. The simulation aims to create a visually intuitive way of understanding how the series of amplitude versus driving frequency graphs are obtained by showing how the displacement of the system changes over time as it transits from the transient to the steady state. A suggested "how to use" the model is added to help educators and students in their teaching and learning, where we explain the theoretical steady-state equation time conditions when the model begins to allow data recording of maximum amplitudes to closely match the theoretical equation, and the steps to collect different runs of the degree of damping. We also discuss two of the design features in our computer model: displaying the instantaneous oscillation together with the achieved steady-state amplitudes, and the explicit world view overlay with scientific representation with different degrees of damping runs. Three advantages of using EJS include: (1) open source codes and creative commons attribution licenses for scaling up of interactively engaging educational practices; (2) the models made can run on almost any device, including Android and iOS; and (3) it allows the redefinition of physics educational practices through computer modeling.