Resistance Force

A force that opposes motion

Sometimes called
drag


http://answers.yahoo.com/question/index?qid=20100320003920AAwsne4

http://www.physicsclassroom.com/class/newtlaws/u2l2b.cfm

http://wiki.answers.com/Q/What_is_resistance_as_a_force

http://www.kids.ct.gov/kids/cwp/view.asp?a=2731&q=330926

Games

http://www.sciencekids.co.nz/gamesactivities/forcesinaction.html