myPhysicsLab vs Step

myPhysicsLab is a free, open-source project with interactive physics simulations and JavaScript classes for building animated models. Simulations run in real time, and users can drag objects or change parameters such as gravity. Its library includes examples such as pendulums, springs, colliding blocks, roller coasters, billiards, and molecular models. Many simulation pages explain the mathematics behind the models. Users can customize simulations with EasyScript or JavaScript in a browser and text editor, then share a setup through a URL that embeds EasyScript. Numeric results can be retrieved through VarsHistory, JavaScript, or collision-data scripts. Downloadable versions can be used offline. The source code is available on GitHub under the Apache 2.0 License. The simulations do not specify measurement units, so values need to be used consistently within each model. Building from source requires TypeScript, esbuild, Perl, and GNU Make. The project began in 2001, and its maker is based in Seattle, Washington.

Step is a free Linux desktop application for exploring physical systems through interactive simulations. Users can change body and force properties while a simulation runs. Supported models include two-dimensional classical mechanics, molecular dynamics, sound waves, and deformable bodies, with particles, damped springs, gravitational and Coulomb forces, rigid bodies, and collision handling. Step calculates unit conversions, expressions, error propagation, and solver error estimates. Explicit and implicit solvers reach 8th order, with optional adaptive timesteps; most require GSL. Graph, meter, and tracer tools visualize results, while a controller changes properties using keyboard shortcuts. Tutorials, example experiments, object information, and an integrated Wikipedia browser provide learning material. More examples can be downloaded through KNewStuff. Expression calculations such as unit conversion require libqalculate. Step is GPL-2.0+ software, and its StepCore library can be used separately. The listed release is Step 26.08.2, released 2026-10-08.