A series of 46 videos covering essential (not basic) concepts in Science, Technology, Engineering and Mathematics subjects, produced by MIT and available for viewing and download on the MIT OpenCourseWare site. The videos are designed for first and second year engineering students.

# gravity

# PhET Interactive Simulations for Science and Math

University of Colorado

Founded in 2002 by Nobel Laureate Carl Wieman.

The simulations are written in Java, Flash or HTML5, and can be run online or downloaded to your computer. All simulations are open source.

“Move the sun, earth, moon and space station to see how it affects their gravitational forces and orbital paths. Visualize the sizes and distances between different heavenly bodies, and turn off gravity to see what would happen without it!”

This simulation makes it easy to understand the relationship between derivative and integral, for example in the case of distance, speed and acceleration.

This one shows what happens when you change one of the the parameters of an equation.