Check out our channel FunScienceDemos: https://www.youtube.com/user/funsciencedemos Jared discusses friction and then uses blocks on a ramp to show us the effects of different surfaces. Follow this link: http://learningscience.org/psc1bpositionmotionobjects.htm to a great page on out companion website learningscience.org. Be sure to check out numbers 5 & 7 to learn more about friction.