Science in Action – Friction – an 18m 42s video.
KS3 Bitesize foundation level – Forces & Motion – a video covering Speed, Balanced & Unbalanced Forces, Forces in Action and the Effects of Forces.
Scientific Eye: Speed & Safety (19m).
Two videos on Weight versus Mass:
Mass, volume, density, and Archimedes:
Buoyancy from Bill Nye:
Scientific Eye: Floating & Sinking (19m 45s).