- http://www.bbc.co.uk/schools/scienceclips/ages/8_9/friction.shtml
- http://pbskids.org/sid/funwithfriction.html
- http://www.racemath.info/forcesandpressure/ks2_friction_b.htm
- http://www.funderstanding.com/educators/coaster/
- http://content3.jason.org/resource_content/content/digitallab/4859/misc_content/public/coaster.html