1K20 Friction# 01 Braking 02 Phonebook Friction 04 Falling Stick 05 Throwing a Basketball 06 Chain Friction 07 Moving Two Fingers under a Meterstick 08 No Tipping Allowed 09 Pulling a Sliding Block 10 Rolling Up-and-Down, Again and Again 11 Rope on a Table 12 Sliding Towel
