Weight, mass, g
http://www.thephysicsaviary.com/Physics/Programs/Labs/ForceGravityBucketLab/index.html
Force, mass, acceleration
F=ma deceleration/friction
https://serc.carleton.edu/dmvideos/players/brass_cylinder_.html?hide_banner=true
Forces and friction
http://physics.bu.edu/~duffy/HTML5/force_motion_1D_friction.html
Investigate F = ma with/without friction
http://www.physicsclassroom.com/Physics-Interactives/Newtons-Laws/Force/Force-Exercise-1
Change masses, friction, measure time
http://www.physicsclassroom.com/Physics-Interactives/Newtons-Laws/Atwoods-Machine