step

Step is an interactive physical simulator. It allows you to explore the physical world through simulations.

Features:

Classical mechanical simulation in two dimensions;
Particles, springs with dumping, gravitational and coulomb forces;
Rigid bodies;
Collision detection (currently only discrete) and handling;
Soft (deformable) bodies simulated as user-editable particles-springs system, sound waves;
Molecular dynamics (currently using Lennard-Jones potential):
- gas and liquid,
- condensation and evaporation,
- calculation of macroscopic quantities and their variances;
Units conversion and expression calculation;
Errors calculation and propagation;
Solver error estimation;
Several different solvers;
Controller tool to easily control properties during simulation;
Tools to visualize results: graph, meter, tracer;
Context information for all objects, integrated wikipedia browser;
Collection of example experiments, more can be downloaded with KNewStuff2;
Integrated tutorials.