Encyclopedia of Earth
Encyclopedia of Earth: Physics & Chemistry: Mass
Defines inertial and gravitational mass, their scientific history, formulas used in their calculation, the definition of weight, units used for mass, and mass as perceived in the theory of special relativity.
Georgia State University
Georgia State University: Hyper Physics: Special & General Relativity
This site from the Georgia State University provides an interesting chart form of the ideas of relativity. Column 1 - Idea, Column 2 - Experiment. Each item is linked to its own page of explanation, which is well done. A nice type of...
Georgia State University
Georgia State University: Hyper Physics: Relativistic Momentum
A clear (as these things go) presentation of the calculation of relativistic momentum. Given with a handy calculator that even calculates the % error. The site goes on to Momentum of a Photon, and to Relativistic Energy in Terms of...