Phet

Physics Education Technology is a program from the University of Colorado that aims to promote education of the principal laws of physics through a series of fun, interactive simulations made with Java.

Projectile trajectories, electromagnetic waves, construction of electrical circuits, the greenhouse effect, and force and friction are just some of the simulations included in Phet. They have others that cover properties of chemistry, like pH level, salts and solubility, particle collision, and more.

Phet creates a direct access icon on your desktop, from with you can access an offline version of the program's official webpage. You can use any web browser you like to explore and run their simulations.