CK-12 Foundation
Ck 12: Flex Book Textbooks: Chemistry Second Edition
[Free Registration/Login may be required to access all resource tools.] A complete, web-based, multi-media textbook covering a wide variety of Chemistry concepts.
Science Education Resource Center at Carleton College
Serc: Flight to Mars: How Long? Along What Path?
Demonstrate how, with the use of orbital mechanics, a space mission to Mars can be planned. Using no more than algebra, Kepler's laws and the formula for the energy of an object in a Kepler orbit, the exercise derives the time for an...